HES 


UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


'e  stamped  beloi 


SOUTHERN  BRANCH; 
UNIVERSITY  OF  CALIFORNIA 

LIBRARY, 

tX>S  ANGELEa  CALIF. 


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RESEARCHES    OX    FtJXGI 


RESEARCHES 
ON    FUNGI 

AN  ACCOUNT  OF  THE  PRODUCTION,  LIBERATION, 

AND  DISPERSION  OF  THE  SPORES  OF  HYMENO- 

MYCETES  TREATED  BOTANICALLY 

AND  PHYSICALLY 

ALSO  SOME  OBSERVATIONS  UPON  THE  DISCHARGE  AND 

DISPERSION  OF  THE  SPORES  OF  ASCOMYCETES 

AND  OF  PILOBOLUS 


BY 

A.    H.    REGINALD    DULLER 

B.Sc.  (LoND.) ;   D.Sc.  (BIRM.);   PH.D.  (LEIP.) 

PROFESSOR    OF    BOTANY    AT    THE    UNIVERSITY    OF    MANITOBA 


WITH  FIVE  PLATES  AND  EIGHTY-THREE  FIGURES  IN  THE  TEXT 


LONGMANS,    GREEN    AND    CO. 

39    PATERNOSTER    ROW,    LONDON 

NEW  YORK,  BOMBAY,  AND  CALCUTTA 

1909 

67S38 

All  rights  reserved 


toi 


TO 

WILHELM  PFEFFER 

UNDER  WHOSE  STIMULATING  GUIDANCE 

THE  AUTHOR  ONCE  HAD  THE 

PRIVILEGE  OF  STUDYING 


PREFACE 

THESE  pages  contain  a  contribution  to  the  physiology,  mor- 
phology, and  physics  of  reproduction  in  the  Hymenomycetes,  and 
also  a  record  of  some  observations  upon  the  discharge  of  spores 
of  'Ascomycetes  and  of  Pilobolus.  Naturally  many  problems  have 

^     been  left   unsolved,  but  I  hope  that  the  new  data  obtained  will 

\^   give  an  added  interest  to  some  of  our  commonest  plants.     The 

delicate    adaptations    of  structure   to   function,   as   revealed   by   a 

study  of  the  fruit-body  of  a  Mushroom,  a  Coprinus  comatus,  or 

^    a  Polyporus,  have  provided  me  with  no  small  cause  for  wonder- 
^      ment   and  delight,  and  they  seem   well  worthy  of  the   attention 

^'  of  all  those  who  desire  to  understand  more  fully  the  vegetable 
world  by  which  they  are  surrounded.  The  value  of  the  more 
purely  physical  work  must  be  left  to  physicists  to  decide.  How- 
ever, as  showing  how  closely  the  various  branches  of  science  may 

^   be  knit  together,  it  is  not  without   interest   that  the  first  direct 

V   test  of  Stokes'  Law  for  the  fall  of  microscopic  spheres  in  air  has 
.   been  carried  out  with  the  help  of  a  lowly  Cryptogam. 

The  research,  which  has  occupied  five  years,  was  preceded  and 

'N  suggested  by  a  systematic  study  of  fungus  species  in  the  field,  in 
which  I  was  much  assisted  by  Geo.  Massee's  British  Fungus  Flora 
and  M.  C.  Cooke's  Illustrations  of  British  Fungi.  During  the 
winters  the  experimental  work  was  carried  on  in  my  own  laboratory 
at  the  University  of  Manitoba,  and  during  the  summers  in  the 
Physics  and  Botanical  laboratories  at  the  University  of  Birming- 
ham. I  have  much  pleasure  in  expressing  my  best  thanks  to 
Professors  Poynting  and  Hillhouse  for  the  facilities  accorded  me. 
I  also  wish  to  acknowledge  my  indebtedness  to  Dr.  Guy  Barlow 


viii  PREFACE 

for  valuable  help  and  criticism  in  the  more  purely  physical 
and  mathematical  parts  of  the  research.  Of  the  photographs  here 
published  ten  were  kindly  made  for  me  by  Mr.  J.  E.  Titley  of 
Four  Oaks,  Warwickshire,  three  each  by  Mr.  J.  H.  Pickard  and 
Mr.  P.  Grafton  of  Birmingham,  and  two  by  Mr.  C.  W.  Lowe  of 
Winnipeg.  They  are  all  acknowledged  in  the  text.  In  the  final 
revision  of  the  proofs,  Mr.  W.  B.  Grove  has  been  good  enough  to 
give  me  the  benefit  of  his  wide  mycological  knowledge  and  experi- 
ence. Lastly,  my  gratitude  is  due  to  the  Birmingham  Natural 
History  and  Philosophical  Society  for  defraying  the  cost  of  three 
of  the  Plates. 

A.  H.  REGINALD  BULLER. 

WINNIPEG,  July  1909. 


TABLE   OF  CONTENTS 

PAGE 

PREFACE vii 

PART   I 

Ax /ACCOUNT  OF  THE  PRODUCTION,  LIBERATION,  AND  DISPERSION  OF  THE 

SPOKES  OF  HYMENOMYCETES  TREATED  BOTANICALLY  AND 

PHYSICALLY 


INTRODUCTION  . 


CHAPTER  I 


The  Hymenium — Basidia  and  Paraphyses — Nuclear  phenomena — The  Colour 
of  Spores — Two-spored  Basidia  in  Cultivated  Varieties  of  Psalliota  cam- 
pestris — Occasional  Sterility  of  Coprinus  Fruit-bodies — Cystidia — Fungus 
Gnats,  Springtails,  and  Mites — Position  of  the  Hymenium — Comparison 
of  the  Basidium  with  the  Ascus— The  Effect  of  Sunlight  upon  Spores  .  6 

CHAPTER  II 

The  Extent  of  the  Hymenium — Principles  underlying  the  Arrangement  of 

Gills  and  Hymenial  Tubes — The  Margin  of  Safety — The  genus  Fomes  .       27 

CHAPTER  III 

The  Functions  of  the  Stipe  and  Flesh  of  the  Pileus— The  Gill-chamber         .       39 

CHAPTER  IV 

Adjustments  of  Fruit-bodies  in  the  Interests  of  Spore-liberation — Lentinus 
lepideus,  Psalliota  campestris,  Polyporus  squamosus,  Coprinus  plicatilis, 
('oprinus  niveus,  and  Coprinus plicatiloides — Reactions  of  Fruit-bodies  to 
Light  and  Gravity — The  Problem  of  Pileus  Eccentricity — Geotropic 
Swinging — Rudimentary  Fruit-bodies 47 

CHAPTER  V 

Spore-deposits— The  Number  of  Spores 79 

CHAPTER  VI 

Macroscopic  Observations  on  the  Fall  of  Spores  of  Polyporus  squamosus .         .       89 


x  TABLE   OF   CONTENTS 

CHAPTER   VII 

PAGE 

The  Demonstration  of  the  Fall  of  Spores  by  means  of  a  Beam  of  Light          .       94 

CHAPTER   VIII 
The  Spore-fall  Period        .         . .         .102 

CHAPTER  IX 

Desiccation    of    Fruit-bodies — A    Xerophytic    Fungus    Flora — The    genus 

Schizophyllum 105 

CHAPTER   X 

External  Conditions  and  Spore-discharge— The  Effect  of  Light— The  Effect 
of  Gravity— The  Effect  of  the  Hygroscopic  Condition  of  the  Air— The 
Effect  of  Heat  —The  Effect  of  Alteration  in  the  Gaseous  Environment 
—The  Effect  of  Anaesthetics 120 

CHAPTER   XI 

The  Violent  Projection  of  Spores  from  the  Hyraenium — Methods  I.,  II.,  III., 

IV.,  and  V 133 

CHAPTER   XII 

The  Mechanism  of  Spore-discharge  .         . 148 

CHAPTER   XIII 
The  Specific  Gravity  of  Spores .     153 

CHAPTER   XIV 

The  Size  of  Spores— Poynting's  Plate  Micrometer 158 

CHAPTER   XV 
The  Rate  of  Fall  of  Spores  and  Stokes'  Law— Appendix         <        .         .         .     164 

CHAPTER   XVI 

The  Effect  of  Humidity  on  the  Rate  of  Fall  of  Spores 179 

CHAPTER   XVII 

The  Path  of  the  Spores  between  the  Gills,  &c.— The  Sporabola— Appendix 

on  the  Motion  of  a  Sphere  in  a  Viscous  Medium,  by  Dr.  Guy  Barlow     .     184 


TABLE   OF   CONTENTS  xi 

CHAPTER   XVIII 

PAGE 

The  Electric  Charges  on  the  Spores 192 

CHAPTER  XIX 
The  Coprinus  Type  of  Fruit-body .196 

CHAPTER   XX 

The  Dispersion  of  the  Spores  after  Liberation   from   the    Fruit-bodies — 

Falck's  Theory 216 

CHAPTER   XXI 

The   Dispersion   of   Spores  by  Animals — Coprophilous   Hymenomycetes— 

Slugs  and  Hymenomycetes        .         .         .         .         .         .         .         .         .     224 

PART  II 

SOME  OBSERVATIONS  UPON  THE  DISCHARGE  AND  DISPERSION  OF  THE 
SPORES  OF  ASCOMYCETES  AND  OF  PlLOBOLUS 

CHAPTER  I 

The  Dispersion  of  Spores  by  the  Wind  in  Ascomycetes — Puffing — The 
Physics  of  the  Ascus  Jet  in  Peziza — The  Fixation  of  the  Spores  in  the 
ASCIIS  of  Peziza  repanda — Comparison  of  the  Sizes  of  Wind-borne  Spores 
in  Ascomycetes  and  Hymenomycetes — The  Helvellacese  ....  233 

CHAPTER   II 

The  Dispersal  of  the  Spores  of  Ascomycetes  by  Herbivorous  Animals  illus- 
trated by  an  Account  of  Ascobolus  immersus — Pilobolus,  Empusa  muscx — 
Lycoperdon — The  Sound  produced  by  the  Discharge  of  Spores  with 
special  reference  to  Pilobolus  .  .  .  .  .  .  .  .  .251 


GENERAL  SUMMARY — 

Part  1 261 

Part  II 268 

EXPLANATION  OF  PLATES  I.-V 270 

PLATES  I.-V To  follow  p.  274 

GENERAL  INDEX  .     275 


PART    I 

AN     ACCOUNT     OF     THE     PRODUCTION,    LIBERATION,    AND 

DISPERSION  OF  THE  SPORES  OF  HYMENOMYCETES 

TREATED  BOTANIC  ALLY  AND  PHYSICALLY 


INTRODUCTION 

THE  researches  recorded  in  Part  I.  were  undertaken  with  the  object 
of  throwing  light  upon  the  production,  liberation,  and  dispersion 
of  tjie  spores  of  Hymenomycetes.  More  especially,  an  effort  has 
been  made  to  find  out  how  the  spores  manage  to  escape  from  the 
hymenial  surfaces  where  they  have  been  produced,  and  how  they 
find  their  way  between  gills,  down  tubes,  &c.,  to  the  exterior  of  the 
fruit-bodies.  By  using  appropriate  optical  methods,  it  has  been 
attempted  to  follow  the  spores  individually  from  the  moment  they 
leave  the  basidia,  to  determine  their  paths  through  the  air,  and  to 
measure  by  accurate  means  their  rate  of  fall.  This  part  of  the 
research  has  led  me  to  the  border-land  where  botany  passes  into 
pure  physics.  Hitherto,  it  appears  that  physicists  have  never  yet 
determined  directly  by  experiment  the  rate  of  fall  of  individual 
microscopic  spheres  with  a  diameter  of  3-10  /*  through  air.1  There- 
fore, by  means  of  observations  on  the  fall  of  spores,  I  have  en- 
deavoured to  test  the  well-known  and  often  assumed  Stokes'  Law. 
In  studying  the  effect  of  external  conditions  upon  the  liberation 
of  spores,  and  in  determining  the  length  of  the  spore-fall  period, 
the  work  has  been  much  simplified  by  two  discoveries.  The  first 
is  that  spore-clouds,  and  even  individual  spores,  can  be  seen  falling 
beneath  a  fruit-body  without  magnification  when  illuminated  with 
a  concentrated  beam  of  light.  Whether  or  not  spores  are  falling 
from  a  fruit-body  can  thus  be  ascertained  in  a  few  seconds.  The 
second  discovery  is  that  practically  all  the  leathery  or  corky  fruit- 
bodies  to  be  found  on  logs,  ie.  those  belonging  to  the  genera  Lenzites, 
Polystictus,  Dtedalea,  Stereum,  &c.,  retain  their  vitality  on  desicca- 
tion for  months  or  years,  and  that,  when  they  are  subsequently 
placed  under  moist  conditions,  the  liberation  of  spores  begins  once 

1  Cf.  the  Appendix  to  Chap.  XV. 


4  INTRODUCTION 

more  within  a  few  hours,  and  continues  for  days  or  weeks.  It  was 
therefore  possible  for  me  to  collect  a  stock  of  these  fruit-bodies  in 
autumn,  to  revive  them  at  will,  and  thus  to  study  the  liberation  of 
spores  throughout  winter  and  spring. 

There  seems  to  be  but  little  literature  dealing  with  the  liberation 
of  spores  of  Hymenomycetes.  Some  observations  of  Brefeld,1  given 
in  a  footnote  in  his  description  of  the  life-history  of  Coprinus  ster- 
corarius,  will  be  mentioned  and  criticised  later  on.  Richard  Falck  - 
has  published  a  paper  on  the  scattering  of  spores  of  Basidiomycetes, 
in  which  he  has  given  an  account  of  the  gradual  accumulation  of 
spore-deposits  on  upper  surfaces  in  closed  chambers.  He  did  not 
succeed  in  actually  seeing  the  spores  in  the  air,  but  his  experiments 
showed  that  they  are  carried  with  remarkable  ease  by  the  slightest 
air-currents.  This  fact  can  be  verified  directly  and  very  simply  by 
means  of  my  beam-of-light  method,  and  rendered  capable  of  mathe- 
matical treatment  by  an  exact  determination  of  the  rates  of  fall  of 
the  spores  in  still  air. 

A  visible  spore-discharge  from  a  fruit-body  has  been  occasionally 
observed  as  a  very  rare  phenomenon  by  a  few  botanists.  To  the 
records  of  Hoffman,  H.  von  Schrenk,  and  Hammer3  will  be  added 
my  own  upon  the  visible  discharge  of  spores  from  fruit-bodies  of 
Polyporus  squamosus. 

In  his  translation  of  Pfeffer's  Physiology  of  Plants,  Ewart 4  added 
a  brief  statement  of  some  of  my  then  unpublished  conclusions  con- 
cerning the  liberation  and  fall  of  spores.  The  evidence  in  support 
of  these  conclusions  is  brought  forward  for  the  first  time  in  this 
book. 

In  an  account  of  the  biology  of  Polyporus  squamosus,  I  recorded 
a  number  of  observations  upon  the  fall  of  spores  in  that  species,  and 
gave  an  illustration  showing  the  paths  taken  by  the  spores  in  falling 
down  the  hymenial  tubes.5  A  subsequent  calculation,  however, 

Brefeld,  Botanische  Untersuchunyen  iiber  Schimmelpilze,  III.  Heft,  pp.  65,  66. 

R.  Falck,  "Die  Sporenverbreitung  bei  den  Basidiomyceten,"  Beitriige  zur 
Bio  ogle  der  Pflanzen,  Bd.  IX.,  Heft  1,  1904. 

For  references,  vide  infra,  Chap.  VI. 

Pfefter,  Physiology  of  Plants,  translated  by  A.  J.  Ewart,  vol.  iii.  1906,  p.  416. 

Buller,  "The  Biology  of  Polyporus  squamosus,  Huds.,  a  Timber-destroying 
Fungus,"  TJie  Journal  of  Economic  Biology,  vol.  i.,  1906,  p.  131. 


INTRODUCTION  5 

has  taught  me  that  the  curves  which  we  shall  refer  to  later  on  as 
sporabolas,  should  have  been  made  to  turn  more  sharply  from  the 
horizontal  to  the  vertical  direction.  This  correction  is  given  in 
Fig.  66  (p.  189). 

The  material  for  the  present  investigation  has  included  more 
than  fifty  species,  chiefly  belonging  to  the  Agaricinese  and  Polyporea3. 
Species  of  Thelephorete  and  of  Hydnese  have  been  used  less  often. 
The  research  has  not  been  extended  to  the  Clavariese,  but  there 
seems  to  be  no  reason  to  expect  that  the  mechanism  for  spore- 
discharge  in  this  group  is  different  from  that  in  those  already 
named.  To  what  extent  my  generalisations  upon  the  liberation  of 
spores  into  the  air  are  applicable  to  the  gelatinous  fungi,  only  further 
investigations  can  decide.  Spore-discharge  was  found  to  take  place 
in  the  normal  manner  in  Hirneola  auricula-judte,  but  the  mode  of 
spore-dispersion  is  not  clear  to  me  in  gyrose  Tremellinene.  In  the 
light  of  my  observations  upon  other  fruit-bodies,  it  seems  difficult 
to  understand  how  spores  produced  on  a  hymenium  which  looks 
upwards  can  escape  into  the  air.  Possibly  only  those  spores  are 
thus  set  free  which  are  developed  on  that  part  of  the  hymenium 
which  is  situated  in  a  vertical  or  downwardly  looking  position. 
Possibly  the  wind  is  not  the  only  agent  in  the  dispersion  of  the 
spores.  This  matter  certainly  requires  further  elucidation.  Un- 
fortunately, gyrose  Tremellinese  so  far  have  not  been  at  my  disposal. 

The  general  result  of  the  observations  recorded  in  this  book 
seems  to  be  that  of  laying  emphasis  on  the  fact  that  the  fruit-bodies 
of  Hyinenomycetes  are  highly  efficient  organs  for  the  production 
and  liberation  of  spores.  In  the  case  of  the  Coprini,  I  believe  that 
the  old  puzzle  as  to  the  significance  of  "  deliquescence  "  has  at  last 
been  solved.  It  can  be  shown,  e.g.  in  Coprinus  comatus,  that  auto- 
digestion  takes  place  for  the  purpose  of  permitting  the  spores  to  be 
liberated  into  the  air,  and  is  correlated  with  several  other  structural 
and  developmental  features  in  the  fruit-bodies  in  question.  It  has 
become  clear  to  me  that,  included  in  the  Agaricineee,  there  are  two 
distinct  fruit-body  types  for  the  production  and  liberation  of  spores 
— the  Mushroom,  or  Psalliota  type,  and  the  Coprinus  comatus  type. 
The  latter  appears  to  have  been  evolved  from  the  former,  and  to  be, 
in  some  respects  at  least,  superior  to  it  in  point  of  efficiency. 


CHAPTER   I 

THE  HYMENIUM— BASIDIA  AND  PARAPHYSES— NUCLEAR  PHENO- 
MENA—THE COLOUR  OF  SPORES— TWO-SPORED  BASIDIA  IN 
CULTIVATED  VARIETIES  OF  PSALL10TA  CAMPESTRIS—OCCA- 
SIONAL  STERILITY  OF  COPRINUS  FRUIT-BODIES— CYSTIDIA— 
FUNGUS  GNATS,  SPRINGTAILS,  AND  MITES— POSITION  OF  THE 
HYMENIUM— COMPARISON  OF  THE  BASIDIUM  WITH  THE  ASCUS 
—THE  EFFECT  OF  SUNLIGHT  UPON  SPORES 

THE  hyinenium  of  most  Hyinenomycetes  is  made  up  of  spore- 
bearing  basidia  and  of  sterile  paraphyses.  In  a  great  many 
species,  it  consists  solely  of  these  two  kinds  of  elements ;  but  in 
a  number  of  others,  cystidia  and  other  specialised  cells  enter  into 
its  structure. 

Basidia  and  Paraphyses. — It  is  a  general  rule,  with  compara- 
tively few  exceptions,  that  each  basidium  produces  four  sterigmata. 
Each  sterigma  tapers  conically,  and  bears  at  its  apex  a  single  spore 
which,  although  sometimes  spherical,  in  most  cases  is  oval  in  shape 
(Fig.  55,  p.  162).  The  spore-wall  in  some  species  bears  spines,  but 
usually  is  quite  smooth.  A  sterigma,  at  the  point  of  attachment  to 
its  spore,  has  an  extremely  small  diameter  which  in  many  instances 
measures  only  0-5  /*  (Plate  I.,  Fig.  34;  Plate  III.,  Fig.  16).  This 
narrow  neck  is  of  great  importance,  for,  when  a  spore  is  set  free, 
the  neck  breaks  across  and  the  spore  is  projected  with  considerable 
violence  straight  outwards  from  the  basidium.1  It  must  be  at 
the  neck  that  the  propelling  force  conies  to  be  exerted. 

The  spores  of  all  Hymenomycetes  are  very  adhesive,  and  on  con- 
tact readily  adhere  to  one  another  or  to  any  object  upon  which  they 
settle.  As  if  to  prevent  them  touching  one  another  during  develop- 
ment and  discharge,  the  four  spores  on  a  basidium  are  borne 
laterally  on  the  sterigmata  in  such  a  manner  that  they  are  situated 
as  far  apart  as  possible  (Plate  I.,  Fig.  3,  a ;  Plate  III,  Fig.  16). 
1  Vide  infra,  Chap.  XI. 


BASIDIA  AND   PARAPHYSES  7 

In  the  Coprini,  the  hymenium,  when  seen  in  face  view,  presents 
to  the  eye  a  remarkably  regular  pattern  (Plate  III.,  Fig.  15). 
The  basidia,  bearing  black  spores,  are  evenly  spaced  between  the 
paraphyses.  Adjacent  basidia,  in  a  zone  proceeding  from  below 
upwards  on  each  gill,  ripen  their  spores  simultaneously.  Hence, 
on  any  small  portion  of  a  gill,  all  the  basidia  are  practically  in 
the  same  stage  of  development.  It  appears  to  be  the  chief 
function  of  the  paraphyses  to  act  as  spacing  agents,  so  that  by 
their  presence  they  prevent  the  spores  belonging  to  adjacent 
basidia  from  coming  into  contact.  The  large,  unicellular  cystidia 
which  are  so  prominent  on  the  swollen  edges  of  the  gills  in  rnany 
species,  e.g.  Coprinus  conwtus,  seem  to  be  significant  in  that  they 
form  suitable  surfaces  of  contact  where  the  gills  touch  one  another 
and  the  stipe.  The  swollen  gill-margins  serve  to  keep  the  gills 
sufficiently  separated  from  one  another,  during  the  development 
of  the  basidia  and  spores  (Plate  I.,  Fig.  5;  Plate  III.,  Fig.  14). 
If  the  gills  were  not  kept  apart,  the  spores  of  opposing  gills  would 
touch  one  another,  and,  owing  to  their  great  adhesiveness,  would 
stick  together.  The  proper  spacing  of  the  gills  during  develop- 
ment, therefore,  is  essential  in  securing  the  efficiency  of  a  fruit- 
body  as  a  spore-producing  organ. 

Excluding  the  highly  specialised  Coprini,  we  find  that  in  the 
Agaricinea3  generally,  as  well  as  in  the  other  groups  of  Hymeno- 
mycetes,  the  basidia  do  not  all  ripen  on  any  part  of  the  hymenium 
simultaneously.  Adjacent  basidia  on  the  gill  of  a  Mushroom, 
in  the  hymenial  tube  of  Polyporus  squamosus,  &e.,  are  at  any 
one  time  in  the  most  diverse  stages  of  development  (Plate  I., 
Fig.  3).  A  basidinm,  bearing  ripe  spores,  may  thus  have 
adjacent  to  it  one  basidium  which  has  shed  its  spores  some 
hours  or  days  previously;  a  second  which  has  spores  in  the  most 
rudimentary  condition ;  and,  possibly,  yet  a  third  upon  which  not 
even  the  sterigmata  have  appeared.  Neighbouring  basidia  with 
ripe  spores  are  often  very  closely  situated,  but  never  near  enough 
to  touch  one  another.  To  what  extent  this  spacing  is  brought 
about  by  the  paraphyses,  or  by  other  basidia,  is  difficult  to  deter- 
mine. Possibly,  the  fact  that,  in  a  Mushroom,  adjacent  basidia 
ripen  and  shed  their  spores  successively,  instead  of  simultaneously, 


RESEARCHES   ON  FUNGI 

permits  of  the  hymenium  being  constructed  with  less  space  devoted 


FlG.  1.—  An  Elm  (Ulmus  montana)  with  five  fruit-bodies  of  Polymrus  touanuuus 
growing  out  from  a  large  wound  surface  where  a  great  branch  had  been  broken 
off.  The  uppermost  fruit-body  has  a  vertical  central  stipe  in  the  middle  of 

AboS  riaXS  R  H'  ?iCkard  ^  *he  Elind       ylUm> 


to  sterile  paraphyses  in  that  species  than  is  required  for  a  Coprinus. 


NUCLEAR  PHENOMENA  9 

The  spacial  arrangements  of  the  basidia  and  their  successive 
development  certainly  require  a  more  detailed  study  in  the  Mush- 
room and  fruit-bodies  of  the  same  type.1 

Nuclear  Phenomena. — The  nuclear  changes  occurring  in  the 
basidia  and  paraphyses  during  development  have  now  been  investi- 
gated by  modern  methods,  and  it  has  been  found  that  each  hymenial 
cell,  when  first  formed,  contains  two  nuclei.2  In  cells  destined  to 
become  basidia,  the  nuclei  fuse  to  form  a  single  nucleus.  By  means 
of  two  successive  bipartitions  the  fusion  nucleus  then  divid.es  into 
four  nuclei,  whereupon  the  sterigmata  and  spores  begin  their 
development.  When  the  spores  have  attained  a  certain  size,  the 
four  nuclei  severally  and  simultaneously  approach  the  four  sterig- 
mata, creep  through  them,  and  pass  into  the  spores,  each  of  which 
thus  becomes  provided  with  a  single  nucleus.  Whilst  making 
their  way  into  the  spores,  it  is  necessary  for  the  nuclei  to  squeeze 
through  the  very  narrow  sterigmatic  necks,  which  feat  is  accom- 
plished by  their  becoming  compressed  into  slender  filaments. 
The  extent  to  which  the  nuclei  suffer  constriction  affords  strik- 
ing evidence  of  protoplasmic  plasticity,  and  may  be  regarded  as 
indicating  that  cytoplasm  may  move  with  considerable  ease 
from  cell  to  cell  through  pits  in  cell-walls.  It  seems  to  be 
highly  probable  that  a  ripening  spore  becomes  cut  oft'  from  its 
sterigma  by  a  cell-wall,  which  eventually  becomes  double.  If 
this  were  not  the  case,  one  might  expect  that  spore-discharge 
would  be  accompanied  by  the  collapse  of  both  spores  and  basidia ; 
but  this  I  have  observed  does  not  occur.3  However,  anatomical 
evidence  of  the  existence  of  the  double  wall  just  before  spore- 
discharge  has  not  as  yet  been  obtained. 

As  the  spores  are  ripening,  the  basidium  is  devoid  of  nuclei. 
However,  its  cytoplasm  remains  living,  and  is  useful  in  main- 

1  The  gills  of  Panseolus  phalxnarum  and  of  some  allied  species  become  finely 
mottled  at  maturity.  Numerous  ripe  spores  are  to  be  found  on  the  darker  areas, 
whilst  those  on  the  lighter  areas  are  still  uncoloured. 

-  I  have  not  made  any  original  investigations  upon  the  cytology  of  the  de- 
veloping hymenium.  The  facts  here  given  in  this  connection  are  taken  from 
the  paper  by  VV.  Ruhland,  "  Zur  Kenntniss  der  intracellularen  Karyogamie  bei  den 
Basidiomyceten,"  Bot,  Zeit.,  1901,  Abt.  I.,  pp.  187-204. 

3   Vide  infra,  Chap.  XTT. 


io  RESEARCHES   ON  FUNGI 

taining  the  turgidity  of  the  cell.  The  gill  of  a  Coprinus  comatus 
was  laid  on  a  glass  slide.  On  looking  at  one  of  the  hymenial 
surfaces  from  above  with  a  microscope,  I  observed  that,  as  the 
gill  began  to  lose  water,  the  four  sterigmata  of  each  basidium 
bent  together  so  that  the  spores  came  into  contact  and  adhered 
to  one  another.  The  turgidity  of  the  basidium  is  important 
therefore  in  that  it  serves  to  keep  the  spores  in  their  proper 
positions  in  space.  In  dry  weather,  spores  —  which  have  a 
relatively  high  ratio  of  transpiring  surface  to  volume — lose  water 
rapidly,  and  a  constant  stream  must  flow  to  them  through  the 
sterigmata  in  order  to  prevent  them  from  collapsing.1 

In  hymenial  cells  destined  to  remain  sterile,  i.e.,  to  become 
paraphyses,  the  two  original  nuclei  with  which  each  is  provided, 
do  not  unite  with  one  another,  but  remain  small  and  show  no 
signs  of  special  activity.  It  is  conceivable  that  at  first  all  the 
hymenial  cells  have  equal  possibilities  of  development,  but  that 
for  some  reason  the  hymenium  becomes  divided  up  physiologically 
into  small  areas,  in  each  of  which  only  a  single  cell  can  develop 
into  a  basidium.  We  might  suppose  that  each  basidium  has  a 
sphere  of  influence  and  by  its  own  development  causes  the  cells 
adjacent  to  it  to  remain  sterile.  The  problem  of  the  spacial 
arrangement  of  basidia  upon  a  hymenium  seems  to  be  essentially  of 
the  same  nature  as  that  of  the  arrangement  of  gills,  hymenial  tubes, 
or  spines  on  pilei,  or  as  that  of  the  arrangement  of  leaves  upon  stems. 

The  nature  of  the  nuclear  fusion  in  basidia  is  a  matter  which 
is  still  under  discussion.  Dangeard2  regards  it  as  morphologically 
and  physiologically  equivalent  to  a  sexual  act,  and  this  view  has 
been  accepted  by  Brefeld.3  The  union  of  the  two  nuclei — called 
karyogamy — must  lead  to  a  doubling  of  the  number  of  chromo- 
somes. The  reduction  of  the  latter  to  one  half — the  number 
which  we  may  suppose  characterises  the  nuclei  of  the  mycelium 
and  of  the  non-basidial  cells  of  the  hymenophore — is  in  all 

1  Cf.  Chap.  XVI. 

2  Dangeard,  "  La  sexualite  chez  les  Champignons,"  Revue  Scientifique,  5e  serie, 
T.  IV.,  1905.     Abstract  in  Bot.  Centralb.,  Bd.  GIL,  1906,  p.  378. 

3  O.  Brefeld,  Untersuchungen  aus  dem  Gesamtgebiete  der  Mycologie,  Bd.  XIV., 
1908,  pp.  246-256. 


NUCLEAR   PHENOMENA  11 

probability  brought  about  in  the  basidium  itself  during  the  two 
successive  bipartitions  of  the  fusion  nucleus.  The  two  original 
nuclei  in  each  basidium  are  not  sisters  but  are  very  remotely 
related  to  one  another.  Investigation  seems  to  show  that  they 
are  derived  by  a  long  series  of  successive  conjugate  divisions  from 
a  pair  of  nuclei,  the  two  members  of  which  come  to  lie  side  by 
side  prior  to  the  development  of  the  fruit-body.  The  nucleus 
which  wanders  into  a  spore  soon  divides  into  two  after  its  entry 
so  that  each  spore  becomes  binucleate.1  As  soon  as  the-  spore 
germinates,  these  two  nuclei  enter  the  germ-tube,  where  they  divide 
at  different  rates  and  not  in  a  conjugate  manner.2  By  further 
nuclear  divisions  the  germ-tube  comes  to  contain  more  than  eight 
nuclei  in  Hypholoma  perplexum,  and  up  to  thirty  in  a  species  of 
Coprinus.3  However,  so  far  it  has  not  been  found  possible  to 
determine  exactly  where  the  first  pair  or  first  pairs  of  nuclei  come 
into  existence.4  In  one  group  of  Basidiomycetes — the  Uredinese — 
Blackrnan5  and  others6  have  observed  that  each  pair  of  nuclei 
which  undergo  fusion  in  the  teleutospore,  is  derived  by  a  long 
series  of  successive  conjugate  divisions  from  a  pair  of  nuclei  brought 
into  existence  by  the  conjugation  of  neighbouring  mycelial  cells. 
The  wall  between  the  two  cells  becomes  perforated  and  the  nucleus 
of  one  cell  wanders  into  the  other  cell.  It  yet  remains  to  be 
decided  whether  or  not  anything  of  a  similar  nature  occurs  in 
the  Hymenomycetes.  In  this  connection  some  interesting  dis- 
coveries may  be  in  store  for  us.  In  species  of  Coprinus,  &c.,  where 
it  has  been  found  possible  to  obtain  fruit-bodies  from  the  mycelium 
produced  from  a  single  spore,  doubtless  cross- fertilisation  between 
two  individual  mycelia  either  does  not  occur  or  is  not  necessary 
for  the  completion  of  the  life-cycle.  Whether  or  not  cross- 

1  Miss  S.  P.  Nichols,  "  The  Nature  and  Origin  of  the  Binucleated  Cells  in  some 
Basidiomycetes,"  Trans,  of  the  Wisconsin  Acad.  of  Sciences,  Arts,  and  Letters,  vol.  xv., 
1904,  pp.  30-70.     Abstract  in  Bot.  Zeit.,  Abt.  II.,  Bd.  LXIV.,  1906,  p.  266. 

2  Ibid.  3  Ibid.  *  Ibid. 

5  V.   H.  Blackman,  "On  the  Fertilisation,  Alternation  of  Generations,  and 
General  Cytology  of  the  Uredinese,"  Ann.  of  Bot.,  vol.  xviii.,  1904. 

6  A.  H.  Christman,  "Sexual  Reproduction  in  the  Rusts,"  Bot.  Gas., vol.  xxxix., 
1905;  also  E.  W.  Olive,  "Sexual  Cell  Fusions  and  Vegetative  Nuclear  Divisions 
in  the  Rusts,"  Ann.  of  Bot.,  vol.  xxii.,  1908. 


12  RESEARCHES   ON  FUNGI 

fertilisation  ever  occurs  in  any  species  of  Hymenomycetes  can 
only  be  decided  by  extended  observations.  At  present  no  Hymeno- 
mycetes seem  to  be  known  which  suggest  that  they  are  hybrids 
produced  from  two  individuals  of  distinct  species.  However,  it 
would  be  interesting  to  plant  the  spawn  of  several  distinct  varieties 
of  the  cultivated  Mushroom  (Psalliota  campestris)  side  by  side  in 
beds  of  manure,  and  to  observe  whether  or  not  under  these  con- 
ditions any  intermediate  fruit-bodies  would  be  produced. 

It  seems  probable  that  the  original  sexual  organs  of  Hymeno- 
mycetes— those  corresponding  to  oogonia  and  antheridia  in  Asco- 
mycetes — have  disappeared,  and  that  a  new  form  of  sexuality  has 
arisen  by  the  fusion  in  the  basidia  of  the  descendants  of  what 
were  originally  merely  vegetative  nuclei.1  This  view  is  supported 
by  the  discovery  of  Miss  'Fraser,2  that  in  Humaria  rutilans,  one 
of  the  Ascomycetes,  normal  fertilisation  by  means  of  sexual  organs 
is  replaced  by  the  fusion  of  vegetative  nuclei  in  pairs — a  process 
analogous  to  that  which  takes  place  in  pseudapogamous  fern  pro- 
thallia  and  also  in  the  Uredineae. 

The  Colour  of  Spores.— The  colour  of  spores  has  long  at- 
tracted attention,  owing  to  the  fact  that  it  has  provided  a  useful 
means  of  subdividing  the  Agaricineae.  It  must  be  admitted, 
however,  that  the  classification  of  this  great  group  according 
to  spore  colour  is  a  purely  artificial  arrangement,  although  it 
fulfils  its  primary  object  of  enabling  the  student  the  more 
readily  to  find  the  name  of  a  particular  species.  There  is  no 
good  reason  for  believing  that  the  Melanospone,  the  Porphyro- 
spone,  the  Ochrosporse,  the  Rhodosporee,  and  the  Leucospone  are 
separate  and  distinct  offshoots  from  a  common  stock,  and  this  has 
been  fully  recognised  by  Hennings  in  his  treatment  of  the  Agari- 
cineae  in  Die  natilrlichen  Pflanzenfamilien  of  Engler  and  Prantl. 

-1  The  vegetative  origin  of  the  fusion  nuclei  in  Hymenomycetes  seems  to  be 
generally  accepted.  Cf.  N.  Bernard,  "  Phenomenes  reproducteurs  chez  les  Cham- 
pignons superieurs,"  Bull,  mens  Assoc.  fr.  Avanc.  Sc.,  1905.  Abstract  in  Bot. 
Centralb.,  Bd.  CL,  1906,  p.  394;  Miss  H.  C.  I.  Fraser,  "Nuclear  Fusions  and 
Reductions  in  Ascomycetes,"  Brit.  Assoc.  Report  for  1907,  p.  688;  also  O.  Brefeld, 
1908,  loc.  ft*.,  p.  256. 

2  Miss  H.  C.  I.  Fraser,  "Contributions  to  the  Cytology  of  Humaria  rutilans," 
Ann.  of  Bot.,  vol.  xxii.,  1908,  p.  42. 


THE   COLOUR   OF  SPORES  13 

In  a  classification  purely  on  the  colour  basis,  we  are  obliged  to  place 
together  such  diverse  black-spored  genera  as  Coprinus,  Anthraco- 
phyllurn,  and  Gomphidius.  Coprinus  is  a  highly  specialised  genus, 
the  fruit-bodies  of  which  are  fragile  and  often  "  deliquescent."  On 
the  other  hand,  the  fruit-bodies  of  Anthracophyllum  are  tough  and 
possess  leathery  or  horny  gills.1  This  genus  is  evidently  much  more 
closely  related  to  the  white-spored  Xerotus,  Lentinus,  and  Marasmius 
than  to  Coprinus.  Gomphidius,  with  its  fleshy  fruit-bodies  and 
thick,  fleshy,  non-deliquescent  gills,  seems  to  be  more  closely 
related  to  the  white-spored  Hygrophorus  than  to  either  Coprinus 
or  'Anthracophyllum.  This  example  will  serve  to  show  that 
spore  colour  by  itself  is  not  a  safe  guide  in  deciding  generic 
relationships. 

During  the  evolution  of  the  Hymenomycetes  there  must  have 
been  an  evolution  of  spore  colour,  and  it  would  certainly  be  very 
interesting  if  some  law  of  progressive  colouration  could  be  dis- 
covered. It  seems  to  me  that  a  fairly  good  case  has  been  made 
out  for  the  view  that,  in  flowers  in  general,  yellow  is  a  more  primi- 
tive colour  than  red,  and  red  more  primitive  than  blue ; 2  but  no 
attempt  to  work  out  the  phylogeny  of  the  colour  of  spores  has 
yet  been  made.  Massee  came  to  the  conclusion  that  the  genus 
Coprinus  is  the  remnant  of  a  primitive  group  from  which  have 
descended  the  entire  group  of  the  Agaric  inese,3  and  he  then  made 
the  deduction  that  since  Coprinus  spores  are  black,  blackness  in 
spore  colour  is  a  primitive  feature.  According  to  this  view,  the 
species  of  Agaricinese  with  yellow,  red,  brown,  purple,  and  white 
spores  have  descended  from  black-spored  ancestors.  In  Chapter  XIX. 
I  shall  bring  forward  what  I  believe  to  be  strong  reasons  for  dis- 
senting from  Massee's  view  as  to  the  ancestral  position  of  the 
Coprini.  If,  as  I  hold,  the  genus  Coprinus  has  been  derived  from 
fungi  having  radially  symmetrical,  stiped,  non-deliquescent  fruit- 
bodies,  with  the  Mushroom  type  of  spore-liberation,  then  Massee's 

1  P.  Hennings  in  Engler  u.  Prantl,  Die  nut.  Pflanzenfamilien,  Teil  I.,  Abt.  1**, 
p.  222. 

2  Grant  Allen,  The  Colours  of  Floicers  (Macmillan  &  Co.),  1891,  pp.  17-60. 

3  G.  Massee,  "  A  Kevision  of  the  Genus  Coprinus,"  Ann.  of  Bot.,  vol.  x.,  1906, 
p.  129. 


14  RESEARCHES   ON  FUNGI 

theory  of  the   primitiveness  of  blackness  as  a  spore  colour  loses 
its  chief  support. 

On  general  grounds,  I  am  inclined  to  regard  colourlessness  as 
the  most  primitive  condition  in  spores.  We  may  well  believe  that 
at  first  the  conidia  were  as  colourless  as  the  basidia  off  which  they 
became  constricted.  It  seems  to  me  probable  that  the  various 
pigments  were  only  gradually  developed,  possibly  by  a  series  of 
mutations.  Many  so-called  black  spores  are  not  truly  black ;  thus 
in  Gomphidius  the  spores  are  smoky-olive,  and  in  Coprinus  atra- 
mentarius  the  spore  powder  has  a  brownish  tinge.  Intermediate 
gradations  of  this  kind  seem  to  suggest  that  blackness  in  spores 
was  not  acquired  all  at  once  but  step  by  step.  This  view  is  further 
supported  by  ontogeny.  Thus  in  Coprinus  comatus  the  spores 
when  very  young  are  colourless;  they  then  become  pinkish,  and 
thereby  turn  the  gills  pink ;  they  then  gradually  become  black. 
In  many  species  of  Coprinus  the  spores  whilst  ripening  become 
brown,  and  the  brown  colour  then  gradually  deepens  into  black. 
As  further  support  for  the  view  that  colourlessness  in  spores  is  a 
primitive  feature  in  Hymenomycetes,  may  be  mentioned  the  fact 
that  five  out  of  the  six  genera  of  Hypochnaceae,1  as  well  as  such 
a  primitive  genus  of  Thelephoreae  as  Corticium,  have  unpigrnented 
spores. 

No  suggestion  has  yet  been  made  as  to  the  significance  of  the 
colours  of  spores.  It  is  certain  that  some  colouring  matters,  e.g. 
those  of  heart-wood,  of  sclerenchymatous  strands  in  the  rhizomes 
of  ferns,  of  carrot  roots,  and  of  the  rhizomorpha  subterranea  of 
Annillarm  mellea,  cannot  be  of  ecological  value,  since  they  are 
developed  in  organs  not  normally  exposed  to  the  light.  Possibly, 
too,  the  colouring  matters  of  spores  are  useless  so  far  as  their 
colour  properties  are  concerned :  they  may  be  merely  bye-products 
of  certain  metabolic  processes.  However,  it  will  shortly  be  shown 
that  sunlight  is  injurious  to  the  spores  of  certain  Hymenomycetes. 
It  therefore  seems  possible  that  the  various  colouring  matters 
deposited  in  spore  walls  may  be  of  value  in  that  they  serve  to 
absorb  injurious  rays  of  light,  thus  preventing  them  from  reaching 
the  living  protoplasm.  If  coloured  spore  walls  are  useful  in  filtering 
1  P.  Hennings,  loc.  «Y.,  p.  114. 


TWO-SPORED   BASIDIA  15 

sunlight,  future  experiments  should  show  that  the  black  spores  of 
Coprini  and  other  Melanospone  suffer  less  from  prolonged  exposure 
to  the  sun  than  the  colourless  spores  of  the  Leucosporse. 

Two-spored  Basidia  in  Cultivated  Varieties  of  Psalliota  cam- 
pestris. — Atkinson1  has  observed  that  the  basidia  of  the  cultivated 
forms  of  Psalliota  campestris  (the  varieties  Columbia,  Alaska,  Bohemia, 
and  others)  are  two-spored,  whereas  those  of  the  wild  field  form  are 
four-spored.  However,  he  found  a  two-spored  variety  of  Psalliota 
campestris  in  the  open — once  on  a  lawn,  and  once  on  the  hillside  of 
a  wooded  ravine  on  the  campus  of  Cornell  University.  My  own 
experience  is  similar  to  that  of  Atkinson.  I  have  noticed  that  the 
basidia  of  the  wild  form  of  Psalliota  campestris  obtained  from  fields 
near  Birmingham,  England,  are  four-spored,  and  that  those  of  a 
cultivated  variety  on  sale  in  Winnipeg  are  two-spored.  I  have  also 
observed  a  two-spored  form  occurring  on  manured  ground  included 
within  the  campus  of  the  University  of  Manitoba.  The  campus 
Mushrooms  differed  considerably  from  the  wild  field  Mushrooms  of 
England  in  that  they  were  more  scaly,  browner,  and  possessed  rela- 
tively very  shallow  gills.  Whether  or  not  normal  two-spored  forms 
of  Psalliota  campestris  occur  in  nature  as  constant  types  still  seems 
to  be  a  matter  of  doubt.  Atkinson  thinks  it  probable  that  the 
cultivated  varieties  of  Psalliota  campestris  originated  as  mutations 
either  from  Psalliota  campestris,  or  from  some  other  species  which 
has  been  confounded  with  it ;  and  with  this  view  I  am  inclined  to 
agree.  Of  two  equally  well  developed  Mushrooms,  one  of  which 
possessed  four-spored  and  the  other  two-spored  basidia,  the  former 
would  doubtless  produce  the  greater  number  of  spores,  and  therefore 
be  the  more  efficient  reproductive  organ.  If  this  be  granted,  the 
two-spored  varieties  of  Psalliota  campestris  may  be  regarded  as 
degenerate  mutations  derived  from  four-spored  ancestors. 

Occasional  Sterility  of  Coprinus  Fruit-bodies. — One  of  the 
most  curious  phenomena  which  has  come  to  my  notice  in 
studying  the  Hymenomycetes,  is  the  occasional  sterility  of 
Coprinus  fruit-bodies.  Strange  indeed  is  the  reproductive  organ 
which  otherwise  undergoes  normal  development  but  fails  in  its 

1  G.  F.  Atkinson,  " The  Development  of  Agaricus  campestris"  The  Botanical 
Gazette,  vol.  xlii.,  1906,  pp.  200-261. 


1 6  RESEARCHES   ON  FUNGI 

essential  function  of  producing  spores.  Instances  of  sterility  of  this 
kind  have  been  noticed  in  two  different  species.  A  board  was  found 
in  a  cellar  infected  with  Coprinus  fimetarius,  var.  cinereus,  and  a 
small  piece  of  it,  bearing  a  young  fruit-body,  was  sawn  off,  brought 
to  the  laboratory,  and  placed  in  a  damp-chamber.  After  further 
development  the  fruit-body  attained  average  size  and  form,  but 
exhibited  the  peculiarity  of  being  yellowish-white  in  colour  instead 
of  ashy  grey.  Upon  examining  the  pileus  with  the  microscope,  I 
found  that  it  was  almost  completely  sterile.  Only  a  few  basidia  had 
produced  spores,  whilst  the  great  majority  had  remained  in  a  rudi- 
mentary condition.  The  normal  basidia  were  found  chiefly  at  the 
pileus  margin,  but  a  very  few  were  sparsely  scattered  over  the 
general  surfaces  of  the  gills.  Two  other  fruit-bodies  subsequently 
appeared  on  the  piece  of  board,  but  in  these  the  spores  were 
developed  in  the  usual  manner.  Coprinus  plicatiloides l  was  grown 
on  sterilised  horse-dung,  from  the  surface  of  which  its  fruit-bodies 
were  produced  in  large  numbers,  several  each  day  for  more  than  a 
month.  At  successive  intervals  about  six  fruit-bodies  came  up, 
which  seemed  to  be  quite  normal  in  size  and  form,  but  which  were 
conspicuous  among  their  companions  by  being  whitish-yellow  instead 
of  grey.  The  microscope  revealed  the  fact  that  the  gills  had  failed 
to  produce  any  spores.  The  basidia,  surrounded  by  large  paraphyses, 
had  remained  quite  small ;  they  did  not  protrude  beyond  the  general 
surface  of  the  hymenium  and,  so  far  as  I  could  observe,  they  had  not 
even  given  rise  to  sterigmata. 

The  cause  of  the  occasional  sterility  of  Coprinus  fruit-bodies  seems 
to  be  somewhat  obscure.  Since,  however,  the  sterile  fruit-bodies  of 
Coprinus  plicatiloides  grew  in  company  with,  and  closely  adjacent 
to,  other  fruit-bodies  which  were  completely  fertile,  it  seems  safe  to 
infer  that  the  sterility  was  not  conditioned  by  temperature,  light, 
heat,  moisture,  or  atmospheric  gases.  Perhaps  the  phenomenon  is 
due  to  some  accident  happening  to  the  mycelium  at  the  time  when 
its  contents  are  being  poured  into  the  young  fruit-body.  It  is  con- 
ceivable that,  if  the  mycelium  attached  to  the  fruit-body  were 
reduced  in  quantity,  the  fruit-body  might  suffer  from  starvation 
during  its  further  development,  and  yet,  in  consequence  of  the 
1  For  nomenclature  of  this  species,  vide  infra,  Chap.  IV. 


CYSTIDIA  17 

continued  absorption  of  water,  still  be  able  to  stretch  its  stipe  and 
expand  its  pileus.  The  diminution  in  the  supply  of  food  materials 
might  lead  to  the  non-development  of  the  basidia.  I  have  attempted 
to  induce  sterility  in  Coprinus  plicatiloides  by  mechanically  dis- 
turbing the  substratum  of  young  fruit-bodies,  and  have  partially 
succeeded.  In  one  experiment  a  large  fruit-body  became  pale 
yellowish-grey  at  maturity,  and  it  was  found  that  the  number  of 
basidia  which  had  developed  in  the  neighbourhood  of  the  stipe  was 
very  much  below  the  normal.  However,  it  must  not  be  supposed 
that  sterile  fruit-bodies  are  produced  only  after  artificial  disturbance 
of  tfre  substratum,"  for  in  one  instance,  in  a  culture  left  undisturbed 
for  some  weeks,  two  fruit-bodies  of  equal  size  came  up  side  by  side 
with  the  bases  of  the  stipes  in  contact,  yet  one  of  them  was  perfectly 
fertile  and  the  other  quite  sterile. 

Cystidia. — The  significance  of  cystidia,  once  thought  by  Corda, 
Hoffman,1  Worthington  Smith,2  and  others,  to  be  male  organs,  still 
seems  not  to  have  been  elucidated  with  any  certainty.  According 
to  Cooke,3  "  The  usual  interpretation  of  the  function  of  cystidia  is, 
that  they  are  simply  mechanical  contrivances  projecting  from  the 
hymenium  and  thus  keeping  the  gills  or  lamelbe  apart."  Possibly 
this  view  may  be  correct  for  certain  species  of  Coprinus,  e.g. 
C.  micaceus,  where  large  cystidia  are  found  on  the  gill  surfaces ;  but 
where  cystidia  coat  the  swollen  gill  edges,  as  in  C.  contains,  we 
may  regard  them  as  packing  cells.  They  form  cushions  where 
the  gills  are  in  contact  with  each  other  and  the  stipe,  and  they 
probably  facilitate  the  separation  of  these  structures  on  the  ex- 
pansion of  the  pileus.  Stress  has  already  been  laid  on  the  necessity 
for  the  provision  of  spaces  between  adjacent  gills  during  develop- 
ment, owing  to  the  adhesiveness  of  the  spores ;  but  these  spaces 
can  be  brought  into  existence,  e.g.  in  C.  comatus,  by  other 
means  than  by  the  production  of  cystidia  (vide  infra,  Chap.  XIX. ; 
Plate  I.  Fig.  5 ;  Plate  III.  Fig.  14).  In  the  genus  Peniophora,  thex 

1  H.   Hoffman,  "Die  Pollinaiien   und  Spermatien  von  Agaricus,"  Rot.  Zeit., 
xiv.,  1856,  pp.  137-48,  153-63. 

2  Worthington  Smith,  "  Reproduction  in  Coprinus  radiatus,"  Grevillea,  vol.  iv., 
1875-6,  pp.  53-65. 

3  M.  C.  Cooke,  Introduction  to  the  Study  of  Fungi,  London,  1895,  p.  41. 

B 


1 8  RESEARCHES   ON   FUNGI 

cystidia  (metuloids),  which  are  very  numerous,  prominent,  and 
encrusted  with  calcium  oxalate,  could  not  possibly  act  as  spacing 
agents ;  for  here  the  hyrnenium  is  smooth.  Possibly,  in  this  genus, 
they  serve  to  protect  the  fruit-bodies  from  slugs  or  other  harmful 
animal  parasites.  The  same  interpretation  might  apply  to  the 
rigid  coloured  setse  of  Hymenochtete,  but  does  not  seem  suitable 
for  those  of  some  species  of  the  woody  genus  Fomes,  e.g.  F.  nigricaws 
and  F.  salicinvis. 

De  Bary's J  investigation  led  him  to  the  conclusion  that  in 
Lactarius  deliciosus  the  cystidia  arise  from  ordinary  hyphse  of 
the  trama,  but  according  to  Massee2  the  cystidia  of  Russula  and 
Lactarius  are  direct  terminations  of  the  laticiferous  system.  Massee's 
view  is  supported  by  the  work  of  Biffen,3  who  found  that  in 
Collybia  velutipes  the  cystidia  form  the  hymenial  endings  of  the 
conducting  hyphse.  In  these  cases,  doubtless,  the  cell  contents 
are  of  importance,  although  exactly  in  what  way  still  remains  to 
be  explained.  In  Russula,  at  least,  they  do  not  seem  to  render 
the  gills  unpalatable  to  slugs,  since  these  animals  are  particularly 
fond  of  the  members  of  this  genus,  and  often  devastate  the  fruit- 
bodies  in  a  wood  to  such  an  extent  that  scarcely  a  single  specimen 
is  left  undamaged. 

Earlier  writers,  Corda  and  others,  stated  that  the  cystidia  of 
the  fleshy  fungi  discharge  their  contents  through  their  apices  in 
the  form  of  drops,  but  de  Bary4  and  Brefeld  could  never  satisfy 
themselves  that  this  is  done  spontaneously.  However,  Massee  and 
Worthington  Smith  have  both  upheld  the  older  view.  According 
to  Massee,5  cystidia,  when  mature,  contain  glycogen  which  is  emitted 
through  the  nipple-like  openings  at  their  apices,  and  poured  over  the 
surrounding  hymenium,  where  it  serves  as  food  for  the  developing 
spores.  Smith6  has  figured  the  cystidia  of  Co^irinus  atramentarius, 
Gomphidius  viscosus,  and  Agaricus  radicatus  as  large,  flask-like 

1  De  Bary,  Comparative  Morph.  and  Biol.  of  Fungi,  English  translation,  1887, 
p.  304. 

2  G.  Massee,  Journ.  Roy.  Micr.  Soc.,  1887,  p.  205. 

3  R,  H.  Biffen,  Journ.  Linn.  Soc.,  vol.  34,  1898,  p.  147. 

4  De  Bary,  loc.  cit.  5  G.  Massee,  loc.  cit. 

6  W.  Smith,  Grevillea,  vol.  x.,  1881,  p.  77  ;  also  Gardeners'  Chronicle,  Sept.  17, 
1881,  p.  367. 


FUNGUS  GNATS  19 

structures  with  narrow  necks  each  provided  with  a  tiny  operculum. 
He  states  that  the  opercula  drop  off  when  the  cystidia  are  mature, 
and  thus  permit  the  cell-contents  to  escape.  According  to  both 
Smith  and  Massee,  the  cystidia  in  many  cases  drop  out  of  the 
hyineniuin  after  they  have  discharged  their  contents.  A  detailed 
confirmation  or  refutation  of  these  various  statements  seems  to 
me  to  be  desirable. 

In  a  recent  paper  Massee1  has  described  two  forms  of  cystidia 
as  occurring  on  the  surface  of  the  gills  in  the  genus  Inocybe — the 
ventricose  and  the  fusoid.  He  states  that  the  tip  of  each  cystidiuru 
becpines  crowned  "with  mucilage,  which  escapes  from  the  interior 
after  the  deliquescence  of  the  thin  portion  of  the  wall  at  its  apex. 

From  the  morphological  point  of  view,  we  may  follow  de  Bary 
in  placing  cystidia  in  the  category  of  hair  formations.  Since  the 
hymenial  hairs  are  of  several  distinct  types,  it  seems  fairly  certain 
from  analogy  with  the  Phanerogams  that  they  have  different 
functions  varying  with  their  structure.  In  some  species  they 
may  be  only  functional  during  the  early  development  of  the  gills, 
whilst  in  others  they  may  be  of  importance  afterwards. 

From  the  point  of  view  of  spore-emission,  cystidia  have  a  limit 
set  to  the  distance  they  may  project  beyond  the  basidia.  Where 
a  hymenial  surface  is  in  a  vertical  plane,  they  only  project  so 
far  that  they  do  not  interfere  with  the  falling  spores.  These  are 
shot  out  horizontally  from  the  basidia  to  a  distance  of  about 
O'l  mm.  They  then  make  a  sharp  turn  and  fall  down  vertically 
(cf.  Fig.  64,  p.  185,  and  Plate  I.,  Fig.  4).  Since  the  cystidia  do 
not  project  so  far  horizontally  as  the  spores  can  be  shot  outwards, 
they  do  not  restrict  the  freedom  of  the  latter  whilst  escaping  from 
the  fruit- body. 

Fungus  Gnats,  Springtails,  and  Mites.— Possibly  in  some 
instances  cystidia  may  have  become  evolved  in  relationship  with 
insects  or  other  small  animals.  Over  one  hundred  and  fifty 
species  of  Mycetophilidje  or  "  Fungus  Gnats  "  have  been  described,2 
and  most  of  them  appear  to  live  on  fungi  only.3  The  whole  group 

1  G.  Massee,  "A  Monograph  of  the  Genus  Inocybe/'  Ann.  of  Bot ,  vol.  xviii., 
1904,  p.  462. 

2  Fred.  V.  Theobald,  An  Account  of  British  Flies  (Dipter.t),  vol.  i.,  1892,  p.  93. 

3  Ibid.,  p.  96. 


20  RESEARCHES   ON   FUNGI 

is  geologically  of  considerable  antiquity,  and  specimens  have  often 
been  preserved  very  perfectly  in  amber.1  At  the  present  day,  in 
the  genus  Mycetophila,  a  female  "  lays  her  eggs  generally  on  the 
under  surface  of  the  pileus,  walking  about  over  the  surface  first 
to  find  a  suitable  place,  then  depositing  the  ova  singly."2  The 
eggs  of  the  Mycetophilidae,  after  being  laid,  quickly  hatch  and 
develop  into  the  well-known  maggots.  These  feed  on  the  stipe, 
the  pileus  flesh,  or  even  the  gills ;  and  they  often  cause  the 
infested  parts  to  become  rapidly  and  prematurely  putrescent. 

The  gills  of  expanded  fruit-bodies  are  frequently  visited,  not 
only  by  Fungus  Gnats,  but  also  by  Springtails  (Collembola)  and 
Mites  (Arachnida).  As  an  instance,  it  may  be  mentioned  that 
on  the  under  side  of  an  unusually  perfect  fruit-body  of  Paxillus 
involutus,  which  had  just  opened,  I  observed  members  of  all 
these  three  groups  present  in  some  numbers.  So  far  as  my 
experience  goes,  it  seems  to  be  rather  the  rule  than  the  exception, 
that  at  least  some  small  animals  are  to  be  found  on  all  large 
fruit-bodies.  When  a  pileus  is  disturbed,  the  Springtails  and 
Mites  run  rapidly  over  the  gill  surfaces,  but  the  Gnats  usually 
fly  away.  Some  fruit-bodies  of  Polyporus  squamosus,  which  were 
growing  on  a  log  and  had  not  yet  become  fully  expanded,  were 
infested  with  small  black  Collembola.  There  were  as  many  as 
fifty  to  the  square  inch,  and  each  one  occupied  a  hymenial  tube 
which  was  just  wide  enough  to  hold  it.  The  Springtails  (genus 
Achorutes),  infesting  the  gills  of  Stropharia  semiglobata  and  some 
other  species  of  Agaricinese,  were  found  to  contain  spores  in  the 
mid-gut.  They  are  therefore  parasites.  It  yet  remains  to  be 
investigated  whether  the  hymenium,  by  means  of  its  hairs,  is 
adapted  in  any  way  to  suit  its  needs  when  visited  by  tiny  animals ; 
or  whether,  on  the  contrary,  Mites  and  Springtails,  «&c.,  are  simply 
to  be  regarded  as  fungus  fleas  which  have  had  no  effect  on  the 
phylogeny  of  their  hosts. 

1  Fossils  have  been  found  in  the  Upper  Oolite  beds  in  the  South  of  England, 
and  also  in  the  Solenhofen  Slates.     More  than  280  species  have  been  obtained 
from  the  Tertiary  in  widely  separated  areas.     Most  of  them  were  discovered  in 
the  ambers  of  Europe  and  America,  the  rock  specimens  being  few  in  comparison 
(ibid,  p.  93). 

2  Fred.  V.  Theobald,  An  Account  of  British  Flies  (Diptera),  vol.  i.,  1892,  p.  94. 


POSITION   OF   THE   HYMENIUM  21 

Position  of  the  Hymenium. — Excepting  a  few  gelatinous  species 
which  require  further  investigation,  it  is  a  general  rule  that  in 
Hymenomycetes  the  hynienium  is  situated  on  the  underside  of 
the  fruit-bodies.  Encrusting  forms,  developing  on  logs  and  twigs, 
usually  produce  their  hymenium  on  the  under  or  lateral  surfaces  of 
the  substratum'.1  That  the  hymenium  should  not  be  developed  on 
a  surface  looking  upwards  is  of  great  importance  for  spore-liberation. 
It  was  found  with  the  beam-of-light  method  that,  if  a  fruit-body  of 
a  Polyporus,  Polystictus,  Lenzites,  Psalliota,  Stereum,  &c.,  is  turned 
OH  its  back,  it  is  unable  to  liberate  its  spores  into  the  air.  It  has 
been  determined  that,  if  the  hymenium  on  the  gill  of  a  Mush- 
room, &c.,  is  made  to  look  directly  upwards,  the  spores  can  be 
shot  upwards  about  0*1  mm.  above  the  basidia.2  This  does  not 
seem  to  be  high  enough  to  permit  of  the  spores,  which  fall  at  the 
rate  of  1-5  mm.  per  second,  being  carried  off  by  moderate  air- 
currents.  Hence,  when  a  hymenial  surface  looks  upwards,  the 
spores  shot  upwards  from  it  fall  back  again  immediately  on  to 
the  hymenium  and  adhere  there.  Even  when  a  fruit-body  is  set 
in  its  natural  position  once  more,  such  spores  never  regain  their 
freedom. 

In  the  great  groups  of  the  Agaricinese  and  the  PolyporeaB, 
the  fruit-bodies  are  characterised  by  having  the  greater  part  of 
the  hymenial  surfaces  disposed  in  almost  vertical  planes.  In  the 
Agaricinese  the  hymenium  is  situated  on  the  surfaces  of  wedge- 
shaped  gills  (Figs.  2  and  3;  also  Plate  I,  Fig.  4);  and  in  the 
Polyporese  it  lines  the  inner  sides  of  cylindrical  or  slightly  conical, 
vertically-placed  tubes  (Fig.  7,  p.  33,  and  Fig.  66,  p.  189).  From 
observations  on  the  paths  and  rates  of  fall  of  individual  spores,  as 
well  as  by  direct  beam-of-light  studies  of  spore-clouds  produced 
from  fruit-bodies  when  tilted  at  various  angles,  I  have  come  to  the 
conclusion  that  it  is  only  when  the  hymenium  is  vertical  or  looking 
downwards  at  a  greater  or  less  angle  that  successful  spore-liberation 

1  I  have  noticed  the  fruit-bodies  of  Irpex  obliquits  growing  on  the  upper  side 
of  an  inclined  tree,  but  the  hymenium  appeared  to  be  irregular.  Falck  (loc.  ctY.) 
grew  abnormal  fruit-bodies  of  Poria  vaporaria  and  Merulius  lacrimans  on  the  upper 
surfaces  of  wooden  blocks  in  the  laboratory. 

•  Vide  infra,  Chap.  XI. 


22 


RESEARCHES   ON  FUNGI 


can  take  place  in  these  groups.  The  mechanism  for  liberating 
spores  is  of  such  a  nature  as  to  limit  the  possible  forms  of  the  fruit- 
bodies  in  question. 

Comparison  of  the  Basidium  with  the  ASCIIS. — The  vertical  or 
downwardly-looking  position  of  the  hymenial  surfaces  of  Hymenomy- 

cetes  may  be  contrasted  with 
the  upwardly-looking  hymenial 
surfaces  of  Discomycetes.  From 
the  physiological  point  of  view, 
the  ascus  in  this  great  group 
of  fungi  is  significant  in  that 
it  is  an  apparatus  by  which 
spores  may  be  liberated  suc- 
cessfully, when  it  looks  upwards. 
It  is  an  explosive  mechanism 
of  considerable  efficiency.  In 
many  instances  it  shoots  out 
its  spores  en  masse  to  a  distance 
of  one  or  several  centimetres, 
and  thus  causes  them  to  be- 
come effectively  separated  from 
the  ascocarp.1  It  seems  to  be 
the  development  of  the  explosive 
ascus  which  has  permitted  of  the 
fruit  -  bodies  of  Discomycetes 
taking  on  their  saucer-  or 
cup-like  shapes.  Here  again, 
as  in  the  Hymenomycetes, 
spore- liberating  mechanism  and 
fruit -body  structure  go  hand 


FlG.  2. — Group  of  young  fruit-bodies  of 
Pleurotus  ostreatnx  (the  Oyster  Fungus) 
growing  from  a  wound  on  the  trunk  of 
a  Beech.  The  gills  are  developing  in 
vertical  planes  in  response  to  a  geo- 
tropic  stimulus.  Photographed  at 
Sutton  Park,  Warwickshire,  by  J.  E. 
Titley.  About  £  natural  size. 


in  hand. 

There  appears  to  be  just  as  strict  a  correlation  between  the 
general  structure  of  an  Agaricus  or  Polyporus  and  its  basidia  as 
between  the  general  structure  of  a  Peziza  and  its  asci.  If  the 
basidia  and  asci  in  these  types  were  interchanged,  each  fruit-body 
would  lose  its  efficiency.  The  spores  could  not  be  liberated,  but 

1  Vide  infra,  Part  II. 


BASIDIA   AND   ASCI 


FlG.  3. — Same  group  of  fruit-bodies  of  Plcurotus  ostrcatux  as  shown  in  Fig.  2, 
photographed  ten  days  later  at  maturity.  The  tops  of  the  pilei  have  now 
become  flattened.  The  thin  gills,  separated  by  interlamellar  spaces,  have 
developed  along  vertical  planes,  and  are  of  various  lengths,  so  as  to  be  very 
compactly  arranged.  The  gills  on  the  stipe  of  the  lowest  fruit-body  have 
been  damaged  by  a  slug.  Photographed  at  Sutton  Park,  Warwickshire,  by 
J.  E.  Titley.  About  ^  natural  size. 


24  RESEARCHES   ON   FUNGI 

would  be  entirely  wasted.  Not  a  single  basidiospore  would  be  shot 
up  far  enough  to  succeed  in  escaping  from  a  Peziza  cup ;  whilst  in 
a  Mushroom  or  Polyporus  the  ascospores,  when  discharged,  would 
strike  and  adhere  to  the  opposite  hymenial  surfaces.  An  upwardly- 
looking,  Peziza-like,  cup-shaped  Hymenomycete,  provided  with 
typical  basidia  and  liberating  its  spores  into  the  air,  is  just  as 
impossible  as  a  Mushroom-  or  Polyporus-shaped  Ascomycete  with 
its  hymenium  composed  of  typical  explosive  asci.  Where,  in  the 
Hymenomycetes,  as  in  the  genus  Cyphella,  the  fruit-body  has  the 
form  of  a  saucer,  a  cup,  or  a  filter  funnel,  with  the  hymenium 
inside,  its  mouth  looks  not  upwards  but  downwards,  so  that  it 
resembles  an  inverted  Peziza.  It  is  true  that  the  conical  wine- 
glass-shaped fruit-bodies  of  the  species  of  the  hymenornycetous 
genus  Craterellus  stand  erect.  Here,  however,  in  contradistinction 
to  Cyphella,  the  hymenium  is  borne  on  the  exterior  of  the  fruit- 
bodies,  whilst  the  interior  is  barren.  The  position  of  the  basidia  of 
a  Craterellus  is  exactly  the  reverse  of  that  of  the  asci  in  the 
erect  wine-glass-shaped  fruit-bodies  of  certain  Ascomycetes.  These 
remarks  may  serve  to  emphasise  the  close  correlation  between  the 
mechanism  for  spore-liberation  and  fruit-body  structure. 

The  Effect  of  Sunlight  upon  Spores. — Some  years  ago,  Massee l 
expressed  the  view  that  the  hymenium  of  the  Hymenomycetes, 
during  progressive  phylogenetic  development,  had  come  to  be 
placed  on  the  lower  sides  of  the  pilei,  instead  of  on  the  upper, 
for  the  purpose  of  concealing  it  from  the  light.  On  the  other 
hand,  my  own  researches  seem  to  show  that  the  position  of  the 
hymenium  has  been  primarily  decided  by  the  necessity  of  the 
basidia  being  so  placed  that  they  can  readily  liberate  their  spores 
into  the  air.  Other,  but  subsidiary,  advantages  accruing  to  the 
hymenium  from  its  position  on  the  lower  side  of  a  pileus,  rather 
than  the  upper,  are:  protection  from  rain,  falling  leaves,  &c.,  and 
undue  transpiration  in  dry  weather. 

The  exact  efl'eot  of  direct  sunlight  upon  the  spores  of  Hymeno- 
mycetes still  remains  to  be  worked  out.  In  the  Clavanea3,  many 
species  live  in  fields,  &c.,  where  their  hymenial  surfaces  are  freely 

1  G.  Massae,  "  A  Monograph  of  B.-itish  Gastromycetes,"  Ann.  of  Bot.,  vol.  iv. 
1889,  p.  2. 


THE   EFFECT   OF  SUNLIGHT  UPON   SPORES        25 

exposed  to  the  sun.  During  their  transportation  by  the  wind, 
spores  must  often  be  exposed  to  sunlight  for  several  hours  together ; 
by  analogy,  therefore,  one  might  expect  them  to  be  fairly  resistant 
to  its  influence.  However,  an  experiment  by  Miss  Ferguson1  tends 
to  show  that  light  has  an  inhibitory  effect  on  the  germination  of 
the  spores  Psalliota  campestris. 

In  order  to  test  the  effect  of  sunlight  upon  the  vitality  of  the 
spores  of  Schizophyllum  commune,  which  are  colourless,  I  proceeded 
as  follows.  A  fruit-body  was  revived  in  the  manner  to  be  described 
in  Chapter  IX.,  and,  when  shedding  spores,  it  was  set  in  a  closed 
chamber  (cf.  Fig.  37,  p.  97),  at  the  bottom  of  which  were  two  glass 
slides  lying  side  by  side.  In  the  course  of  a  night  the  slides  became 
thinly  and  evenly  coated  with  a  spore-deposit,  and  next  morning 
they  were  removed  from  the  chamber.  One  of  them  was  then 
supported  by  a  clamp-stand  so  that  it  was  freely  exposed  to  the 
direct  action  of  the  sunlight  streaming  through  a  window  in  the 
laboratory,  and  the  other  was  kept  in  the  dark.  The  temperature 
of  the  laboratory  was  about  19°  C.  Tests  for  germination  were  made 
by  placing  the  spores  in  hanging  drops  of  a  neutralised  nutrient 
medium  consisting  of  1  per  cent,  glucose,  1  per  cent,  peptone, 
0-3  per  cent,  meat  extract,  0-5  per  cent,  sodium  chloride,  and  10  per 
cent,  gelatine.  The  ring  chambers  containing  the  drops  were 
partially  filled  with  distilled  water,  and  were  kept  in  the  dark. 
Comparative  tests  made  during  the  month  of  April  showed  that 
spores  which  had  been  exposed  to  sunlight  for  eight  hours  germi- 
nated more  slowly  than  spores  which  had  been  exposed  to  sunlight 
for  two  hours,  and  these  more  slowly  than  those  which  had  been  kept 
in  the  dark.  Spores  kept  in  the  dark  germinated  about  twenty 
hours  sooner  than  those  which  had  been  exposed  to  sunlight  for 
seven  or  eight  hours.  After  three  days  the  mycelia  produced  from 
spores  which  had  been  kept  in  the  dark  were  much  more  advanced 
than  those  which  had  been  produced  from  spores  which  had  been 
exposed  to  sunlight  for  periods  of  one,  two,  three,  six,  seven,  and 
eight  hours  respectively.  It  was  also  found  that  exposure  of  the 

1  Miss  M.  C.  Ferguson,  "  A  Preliminary  Study  of  the  Germination  of  the 
Spores  of  Agaricus  campestris  and  other  Basidiomycetous  Fungi,"  C7.S.  Dep.  of 
Agric.,  Bureau  of  Plant  Industry,  Bull.  No.  16,  1902,  p.  21. 


26  RESEARCHES   ON   FUNGI 

spore-deposits  to  sunlight  resulted  in  a  marked  diminution  in  the 
proportion  of  germinating  spores.  This  series  of  experiments, 
together  with  three  others,  has  led  me  to  the  conclusion  that,  when 
dried  spores  of  Schizophyllum  commune  are  exposed  to  direct 
sunlight  for  a  few  hours,  a  certain  proportion  of  them  are  rendered 
incapable  of  germination,  whilst  those  which  germinate  do  so  more 
slowly  than  dried  spores  kept  in  darkness.  Subsequent  experiments 
showed  that  the  spores  of  Dxdalea  unicolor  are  affected  by  sunlight 
in  the  same  manner  as  those  of  Schizophyllum  commune.  From 
the  point  of  view  of  spore-dispersion,  the  experiments  seem  to 
indicate  that  the  spores  of  these  fungi,  when  drifting  about  in  the 
air,  may  survive  exposure  to  sunlight  for  a  whole  day,  and 
that  they  may  subsequently  germinate,  although  with  diminished 
vitality.1 

1  The  injurious  effect  of  sunlight  upon  the  development  of  pathogenic  bacteria 
is  now  well  known.  In  the  case  of  fungi,  Elving  has  shown  that  the  spores  of 
Aspergillus  ylaucus,  and  Laurent  that  those  of  Ustilago  carbo,  are  killed  by  long 
exposure  to  sunlight.  Pfeffer's  Physiology  of  Plants,  English  translation,  vol.  ii. 
p.  247. 


NOTE. — Since  this  chapter  was  set  up,  W.  B.  Grove  has  called  my  attention 
to  the  fact  that  he  has  recorded  (The  Flora  of  Warwickshire,  Fungi,  1891, 
p.  419)  the  occurrence  of  a  fruit-body  of  Stropharia  semiylobata  with  the  gills 
white  owing  to  the  non-development  of  the  spores,  but  otherwise  perfect. 


CHAPTER    II 

THE  EXTENT  OF  THE  HYMENIUM— PRINCIPLES  UNDERLYING  THE 
ARRANGEMENT  OF  GILLS  AND  HYMENIAL  TUBES— THE  MARGIN 
OF  SAFETY— THE  GENUS  FOMES 

THE  Hymenomycetes  are  classified  in  subdivisions  corresponding 
in  the  main  with  the  manner  in  which  the  pileus  is  arranged  in 
relation  to  the  hymenial  surfaces.  Only  in  the  Thelephorea?,  some 
Tremelh'nea?,  and  the  Exobasidiinese  is  the  hymeniuui  smooth  and 
flat,  whilst  in  the  Agaricinere  it  is  arranged  upon  gills,  in  the 
Polyporere  in  tubes,  in  the  Hydne«3  upon  spinous  prolongations, 
and  in  the  Clavariese  upon  the  exterior  of  more  or  less  numerous 
branches  of  the  fruit-body. 

The  various  forms  of  fruit-bodies  may  be  explained  in  their 
evolutionary  aspect  on  the  supposition  that  a  chief  factor  in  their 
survival  has  been  the  advantage  arising  from  the  production  of 
a  relatively  large  number  of  spores  with  a  relatively  small  expendi- 
ture of  fruit-body  material  and  energy.  The  gills,  spines,  tubes,  &c., 
all  have  the  same  significance,  namely,  that  of  increasing  the  extent 
of  the  hymenium  which  a  fruit-body  may  bear.  The  same  end  has 
been  attained  by  different  means.  One  can  easily  imagine  how, 
beginning  with  the  Thelephorese  with  smooth  and  flat  hymenial 
surfaces,  the  more  highly  complex  fruit-bodies  of  the  Agaricinea^, 
the  Polyporese,  the  Hydnere,  and  the  Clavariese  have  been  evolved. 
The  principle  of  folding  to  increase  surface  is  well  illustrated  in 
these  four  groups.  Perhaps  every  possible  means  of  economically 
increasing  hymenial  surface,  consistent  with  the  liberation  of  the 
spores,  has  been  exhausted  by  them. 

In  order  to  obtain  more  precise  information  with  regard  to  the 
advantage  obtained  by  the  production  of  gills,  spines,  tubes,  &c.,  a 
number  of  calculations  have  been  made. 

Let  A  be  the  area  of  the  flat  surface  on  the  underside  of  a 


28  RESEARCHES   ON   FUNGI 

fruit-body,  when  gills,  tubes,  or  spines  have  been  removed.      Let 


FlG.  4. — Fruit-body  of  Polyporm  squamosus  nearly  full-grown  ;  upper  surface  covered 
with  brown  scales.  The  full  length  of  the  stipe  is  photographed.  Photographed 
by  R.  H.  Pickard.  £  natural  size. 

H  be  the  area  of  the  hymenium  upon  the  gills,  tubes,  or  spines. 

TT 

Then  the  ratio  —  gives  the  increase  of  surface  of  the  hymenium 


THE   EXTENT   OF   THE   HYMENIUM  29 

for    which   the   gills,   tubes,  or    spines    are    responsible.      Let    the 


FIG.  5. —  Under  surface  of  fruit-body  of  Polyportts  sffuanioxus  nearly  full-grown, 
showing  the  pores  of  the  hymenial  tubes  and  the  reticulations  on  the  stipe.  The 
fruit-body  was  photographed  immediately  after  it  was  cut :  the  involution  of  the 
edge  of  the  pileus  is  quite  natural.  Photographed  bv  R.  H.  Pickard.  ^  natural 
size. 

specific  increase  of  hymenial  surface,  due  to  the  presence  of  gills, 


3o  RESEARCHES   ON   FUNGI 

tubes,   or  spines   in   any   fruit-body,   be   represented    by   the    con- 
traction Sp.  Inc. 


Then 


Sp.  Inc.  =  ~. 


The  value  of  the  specific  increase  has  been  measured  in  a  few  instances. 

For  species  of  Agaricine;e  the  number  of  gills  was  counted  and 
the  gill-systems  studied.  The  number  of  gills  of  each  size  was 
determined.  A  few  gills  of  each  size  were  dissected  off  the  fruit- 
body,  placed  on  paper,  and  drawn.  The  paper  drawings  were  then 
cut  out  with  scissors,  and  their  area  determined  by  weighing  them 
against  squares  of  paper  marked  out  in  square  millimetres.  The 
fact  that  each  gill  has  two  sides  was  taken  into  account.  With  the 
data  thus  obtained  the  total  area  of  the  gills  could  be  calculated. 
The  value  of  A  was  calculated  from  measurements  of  the  diameters 
of  the  pileus  and  of  the  stipe. 

Full-grown  specimens  yielded  the  following  results  :  — 


Species. 

Diameter  of 
Pileus  in 
Millimetres. 

Specific  I  lie-reuse  of 
Hymenial  Surface 
due  to  the  Production 
ol  Gills. 

Russula  citrina    . 

63 

7-0 

Amanita  rubescens      . 

50 

10-0 

>i               »              ... 

76 

12-2 

Armillaria  mellea         .         . 

76 

12-8 

Tricholoma  personatum 

127 

16-0 

Hypholoma  sublateritium  . 

76 

17-5 

Psalliota  campestris    . 

98 

20-04 

As  an  illustration  of  the  method  of  calculating  specific  increase, 
details  for  the  specimen  of  Tricliolomci  persona  turn,  will  be  given. 

Diameter  of  pileus  =  127  mm. 
Diameter  of  stipe    =    28     „ 

Hence,  the  area  of  the  underside  of  the  pileus,  with  the  gills 
removed,  exclusive  of  the  part  occupied  by  the  stipe,  =  12672'S 
-616  mm.2,  or  A  =120-1  cm.2. 

Number  of  primary  gills  =  101 
„  „  secondary  „  =  101 
„  „  tertiary  „  =  202 
„  ,,  quaternary  ,,  =  404  approximately. 


THE   EXTENT   OF   THE   HYMENIUM  31 

By  the  weighing  method  already  described,  the  area  of  the  gills, 
including  both  sides,  i.e.  H,  was  determined  to  be  1942  cm.2 
approximately. 

Hence,  Sp.  Inc.  =  — ~  =  16  approximately, 

i.e.  the  fruit-body  had  sixteen  times  more  hymenial  surface  than 
it  would  have  had  if  the  underside  of  the  pileus  had  not  been 
produced  into  gills. 

In  the  case  of  the  Mushroom,  the  gills  on  one  quarter  of 
the  ^pileus  were  isolated  one  by  one,  and  their  outlines  marked 
out  on  paper.  The  figures  were  then  cut  out  and  weighed 
against  paper  ruled  into  square  millimetres.  The  area  so  deter- 
mined was  multiplied  by  four,  and  thus  the  whole  surface  area 
of  the  gills  obtained. 

From  the  above  table  it  will  be  seen  that  the  common  field 
Mushroom  has  the  highest  specific  increase,  namely  20.  This  is 
not  surprising,  for  field  Mushrooms  have  deep  gills  closely  packed 
together  (cf.  Plate  IV.,  Fig.  25).  Russida  citrina,  on  the  other 
hand,  has  much  shallower  gills  of  one  length  only,  which  are  placed 
at  some  distance  apart.  The  specific  increase  in  this  species  is 
consequently  very  small :  it  is  only  7,  i.e.  one-third  of  that  of  the 
Mushroom.  Again,  it  is  clear  that  with  pilei  of  equal  diameters. 
Hypholoma  sublateritium  has  considerably  more  gill-surface  than 
either  Amanita  rubescens  or  Armillaria  mellea.  If  we  take  the 
specific  increase  of  gill-surface  as  a  test,  it  seeins  fair  to  conclude 
that  of  the  fungi  investigated,  the  greatest  morphological  advance- 
ment is  exhibited  by  Psalliota  campestris  and  Hypholoma  sub- 
lateritium,  and  the  least  by  Russula  citrina. 

In  the  Polyporete  the  formation  of  hymenial  tubes  often 
leads  to  a  considerable  increase  in  the  spore-bearing  area. 
The  amount  of  increase  depends  upon  the  length  and  breadth 
of  the  tubes.  In  three  species  the  specific  increase  has  been 
measured. 

Polyporus  squamosus  (Figs.  1  and  4-7). — In  the  specimen 
examined  it  was  found  that  in  the  middle  of  the  pileus  there  were 
22  tubes  to  each  square  centimetre.  Each  tube  on  the  average 


32  RESEARCHES   ON   FUNGI 

was  9  mm.  long,  and  possessed  a  perimeter  at  its  base  of  6  mm. 
Hence,  the  area  of  hymenium  for  each  square  centimetre  =  9  x  6  x  '22 
=  1188  mm.2  approximately.  Therefore,  for  1  cm.2,  =100  mm.2, 

•I  -I  Q  Q 

we  find  that  the  specific  increase  = =  11*8  approximately. 

In  most  specimens  of  the  fungus  the  tubes  do  not  attain  a  length 
of  9  mm.  The  specific  increase  is  therefore  usually  less  than  11-8. 
By  comparison  with  the  results  in  the  table  given  above,  it  may  be 
concluded  that  many  Agaricineaj  have  a  larger  specific  increase  than 
Polyporus  squamosus.  However,  this  species  has  unusually  wide 
tubes.  When  the  tubes  are  very  narrow,  as  in  the  cases  of  Fomes 
vegetus  and  F.  igniarius,  now  to  be  discussed,  it  is  found  that 


FIG.  fi. — View  of  part  of  the  underside  of  a  mature  fruit-body  of  Polyporus  tquamonus 


which  was  2  ft.  2  in.  across.     The  openings  of  the  hy menial  tubes  are  polygonal. 


the  specific  increase  may  be  much  greater  than  that  in  any  of  the 
gilled  fungi. 

Fomes  vegetus. — The  fruit-bodies  are  perennial  and  produce 
a  layer  of  tubes  annually  (Fig.  11).  In  the  specimen  examined  it 
was  found  that  for  one  year  there  were  2080  tubes  to  1  square  cm. 
The  length  of  each  tube  on  the  average  was  12  mm.  and  the 
diameter  0-17  mm.  Hence,  the  area  of  the  hymenium  for  each 

square     centimetre  =  12  (^  x  0-17  jx  2080  =  14830-4     mm.2    approx. 

Therefore,  for  1  cm.2,  =  100  mm.2,  we  find  that  the  specific  increase 

—  =  148   approximately.      In   the   specimen   examined   three 


THE  EXTENT  OF  THE  HYMENIUM 


33 


layers  of  tubes  had  been  produced,  and  these  possessed  a  total 
vertical  length  of  40  min.  Hence,  taking  the  three  years  together, 
the  total  specific  increase  amounted  to  493. 

Fomes  igniarius. — In  this  species  also,  the  fruit-bodies  are  per- 
ennial and  produce  successive  layers  of  tubes.  In  a  large  specimen 
it  was  found  for  one  layer  that  in  1  sq.  cm.  the  number  of  tubes 
was  2000.  The  breadth  of  each  tube  on  the  average  was  O'lo  mm. 
and  the  length  4  mm.  Hence,  the  area  of  hymeniuin  for  each 

square  centimetre  =  4  (  — x  0-15^  x  2000  =  3800  mm.2  approximately. 

OQrjTi 

Therefore,  for  1  cm.2,  =100  mm.2,  the  specific  increase  =  ^  =  38 
approximately.  In  the  specimen  examined  there  were  twenty-five 


FIG.  7. — View  of  part  of  a  transverse  section  through  the  middle  of  a  mature 
fruit-body  of  Polyporus  squamotus.  The  hymenial  tubes  are  directed  down- 
wards. Natural  size. 

layers  of  tubes,  having  a  total  thickness  of  100  mm.  For  the  total 
period  of  growth,  therefore,  the  specific  increase  amounted  to  the 
high  value  of  942. 

From  the  figures  just  given,  which  show  that  in  one  year's 
growth  the  specific  increase  for  a  specimen  of  Fomes  ignarius  was 
approximately  38,  and  for  one  of  F.  vegetus  approximately  148, 
it  is  clear  that  the  perennial  Polyporeae  with  narrow  tubes  produce 
much  more  hymenial  surface  for  a  given  area  of  pileus  than  any  of 
the  Agaricinea3.  The  specific  increase  for  Psalliota  campestris,  which 
was  the  highest  in  the  Agaricineoe  investigated,  was  only  20*04. 


34  RESEARCHES   ON  FUNGI 

We  have  seen  that  in  the  Agaricineae  the  extent  of  the 
hymenium  has  been  increased  by  the  production  of  radial  wedge- 
shaped  gills  with  vertical  median  planes,  so  that  the  fruit-bodies 
are  characterised  by  an  admirable  compactness.  However,  certain 
principles  underlying  the  spacing  of  the  gills  in  reference  to  one 
another  still  require  an  elucidation.  The  gills  are  usually  crowded 
together  on  the  underside  of  a  pileus.  Two  adjacent  gills,  how- 
ever, must  be  a  certain  distance  apart  in  order  to  permit  of  the 
liberation  of  the  spores.  It  will  subsequently  be  shown1  that  for 
Psalliota  campestris,  &c.,  the  spores  are  actually  shot  horizontally 
for  about  0-1  mm.  into  the  interlamellar  spaces  before  their  paths 
of  movement  become  vertical.  Two  adjacent  gills,  where  they  are 
closest  to  one  another,  i.e.  near  the  pileus  flesh,  must  therefore  be 
separated  from  one  another  by  a  distance  which  at  least  just 
exceeds  Ol  mm.  In  the  Mushroom  the  minimum  space  between 
the  gills  was  actually  found  to  be  about  0-2  mm.  (Plate  I.,  Fig.  4). 
Probably  nearly  50  per  cent,  of  this  should  be  regarded  as  a 
margin  of  safety.  When  a  mature  pileus  is  tilted  slightly,  so  that 
the  plane  of  the  flesh  is  no  longer  horizontal,  the  gills,  displaced 
from  their  vertical  planes,  react  to  the  stimulus  of  gravity  by 
growth  in  such  a  manner  that  they  quickly  come  to  take  up 
vertical  positions  once  more.2  This,  however,  entails  a  reduction 
in  the  margin  of  safety,  for  the  spaces  between  the  gills  become 
narrowed.  If  the  pileus  is  tilted  beyond  a  certain  amount,  it  neces- 
sarily follows  that,  when  the  gills  have  adjusted  themselves,  the 
margin  of  safety  must  have  disappeared  altogether.  This  must  lead 
to  a  diminution  in  the  number  of  spores  escaping  from  the  pileus. 

In  the  Mushroom,  judging  from  a  study  of  gill-dimensions  as 
embodied  in  Plate  I.,  Fig.  4,  the  margin  of  safety  would  not  be 
used  up  until  the  pileus  had  been  tilted  to  an  angle  of  about  30°. 
In  this  instance,  and  probably  quite  generally  for  Agaricinese,  pro- 
vided only  that  the  gills  have  taken  up  vertical  planes,  just  as 
many  spores  can  be  liberated  from  a  slightly  tilted  as  from  an 

1  Vide  infra,  Chap.  XI. 

*  Cf.  A.  H.  R.  Buller,  "  The  Reactions  of  the  Fruit-bodies  of  Lentinus  lepideus, 
Fr.,  to  External  Stimuli,"  Ann.  of  Bot.,  vol.  xix.,  1905,  p.  432.  Also  vide  infra, 
Chap.  IV. 


THE   ARRANGEMENT   OF   GILLS  35 


untilted  pileus.  This  arrangement  must  be 
of  some  value,  for  in  woods  and  fields  slightly 
tilted  pilei  with  vertical  gills  are  quite  com- 

monly  met  with.  \  / 

It  is  now  clear  that  two  adjacent  gills  *> 

must  be  at  least  a  certain  minimum  distance 
apart  to  permit  of  the  successful  liberation 
of  the  spores.  It  is  equally  clear,  however, 

that  when  the  space  between  two  gills  ex-  r1 ^ 

ceeds  a  certain   maximum   their  arrange-  V * 

merit  is  a  wasteful  one,  for  the  underside  ° 

of  the  pileus  is  then  not  being  used  up  to 

the  best  advantage.    The  gills  of  Agaricineae 

are  disposed  radially,  so  that  in  passing  from 

the  stipe  to  the  edge  of  the  pileus  they 

necessarily   diverge.     Near   the   stipe  two 

adjacent  gills  may  be  economically  spaced. 

Further  from  the  stipe,  however,  owing  to 

divergence,  their  spacing  becomes  wasteful. 

There  is  much  more  room  left  between  them 

than  is  necessary  for  the  liberation  of  the 

spores,  and  for  the  provision  of  an  adequate 

margin  of  safety.     This  defect  is  obviated 

almost  entirely  in  most  Agaricinese  by  the 

introduction  of  shorter  gills  between   the 

longer  ones,  in  succession,  proceeding  from 

the  stipe  to  the  pileus  periphery  (Fig.  8). 

In  some  specimens  of  Marasmius  oreades 

it  was  found  that  the  gills  were  of  three 

different  lengths,  and  that  in  a  specimen 

of  Tricholoma  personatum  they  were  of  four 

different  lengths.     The  complexity  of  the 

gill-system  is  usually  greatest  in  pilei  with 

large   diameters.      Good   examples   of  the 

economical   arrangement   of  gills,  so   that 

the  space  between  any  adjacent  two  shall  Flo.8._As(,,,,,of,iiis removed 

never  exceed   a  certain  maximum   width,       SaShrSSi  $Soio*  *£$?• 

<rw).    Natural  size. 


36  RESEARCHES   ON  FUNGI 

and  yet  never  be  less  than  a  certain  minimum  width,  are  seen 
in  the  Oyster  Fungus  (Pleurotus  ostreatus,  Figs.  2  and  3)  and 
in  the  Mushroom  (Fig.  9  and  Plate  IV.,  Fig.  25).  Certain  species 
of  Russula  have  gills  which  are  all  of  one  length,  with  the 
exception  of  very  occasional  shorter  ones  (Fig.  10).  Since  the 
gills  in  the  fully-expanded  fruit-bodies  diverge  considerably  in 


FlG.  9. — Psalliota  campestris.     Part  of  FlG.  10. — The  pileus  of  Russula  nigricans — 
a  pileus  photographed  from  below,  an  Agaric  iu  which  the  gills  are  very 

showing  that  the  gills  are  accu-  coarsely  spaced.     The  stipe  is  maggot- 

rately  adjusted  so  that  they  look  eaten.     Reduced  to  £  natural  size, 

directly  downwards.   Natural  size. 

passing  from  the  stipe  to  the  margin  of  the  pileus,  their  arrange- 
ment appears  to  be  relatively  imperfect. 

The  principles  underlying  the  arrangement  of  the  gills  of  the 
Agaricinese  doubtless  also  apply  to  the  arrangement  of  the  hymenial 
tubes  beneath  the  pilei  of  species  of  Polyporese.  Other  things 
being  equal,  the  greatest  economy  is  effected  when  the  tubes  are 


THE   GENUS  FOMES  37 

as  numerous  as  possible,  for  this  entails  a  corresponding  increase 
of  hymenial  surface.  The  diameter  of  the  tubes,  however,  must 
always  be  sufficiently  wide  to  permit  of  the  liberation  of  the  spores. 
Since  these  are  shot  outwards  horizontally  into  the  tubes  for  a 
distance  of  about  O'l  mm.,1  the  tubes  can  never  be  less  than  this 
in  diameter.  In  species  of  Polystictus  and  Foines,  where  the  width 
of  the  tubes  is  about  0-2-0-25  mm.,  the  ultimate  reduction  con- 
sistent with  safety  seems  to  have  been  attained. 

The  genus  Fomes,  from  the  point  of  view  of  efficiency  in  the 
production  and  liberation  of  spores,  may  be  looked  upon  'as  having 
fruit-bodies  of  a  highly  specialised  kind.  In  the  first  place  the  fruit- 
bodies  are  perennial.  This  is  economical,  for  the  old  flesh  is  used 


FlG.  11. — Fomes  applanatus  (~F.  veyetus).  Vertical  section  through  a  fruit-body 
three  years  old.  A  new  layer  of  hymenial  tubes  was  produced  each  year. 
Reduced  to  £  natural  size. 

each  year  to  support  new  hymenial  tubes,  and  does  not  function 
only  once,  as  in  the  case  of  such  annual  fruit-bodies  as  Polyporus 
squamosus,  or  those  of  the  Agaricinese,  the  Hydnese,  the  Clavariete, 
or  the  Tremellineoe.  Again,  most  of  the  Fomes  fruit-bodies  are  very 
hard  and  "  woody,"  possess  no  stipes,  and  are  attached  by  a  broad 
surface  to  the  wood  on  which  they  are  produced  (Fig.  11).  This 
gives  them  extreme  rigidity,  so  that  even  in  the  course  of  years 
accidents  are  little  likely  to  injure  them.  The  extreme  rigidity  also 

1  Vide  infra,  Chap.  XI. 

67838 


38  RESEARCHES   ON   FUNGI 

ensures  that  the  very  narrow  hyinenial  tubes  shall  be  kept  exactly 
in  the  vertical  position.  The  importance  of  this  is  obvious  when  it 
is  realised  that  even  a  very  slight  tilt  of  the  tubes  would  prevent  the 
spores  from  escaping  from  them.1  Further,  the  fruit-bodies  can 
withstand  uninjured  the  severest  frosts  of  winter,  and,  judging  from 
some  experiments  made  with  Fomes  igniarius,  can  recover  after  pro- 
longed desiccation.2  Lastly,  they  have  extremely  narrow  hy menial 
tubes.  This,  as  we  have  seen,  involves  a  great  increase  of  spore- 
bearing  surface.  Taking  into  account  the  manner  in  which  the 
spores  are  discharged  from  the  basidia  in  Polyporese  (Fig.  66,  p.  189), 
it  would  seem  that  for  F.  vegetus  and  F.  igniarius  the  width  of  the 
tubes  is  so  small  that,  after  allowing  for  a  small  margin  of  safety, 
it  has  almost,  if  not  quite,  reached  its- limit. 

The  more  liable  a  polyporaceous  fruit-body  is  to  become  slightly 
tilted,  owing  to  developmental  changes,  transpiration,  the  accumula- 
tion of  rain-water  on  its  upper  surface,  the  visits  of  birds,  &c.,  the 
greater  is  the  advantage  of  wide  hymenial  tubes  over  narrow  ones  in 
liberating  the  spores.  Perhaps  it  is  for  this  reason  that  the  tubes  in 
the  soft  and  wide-spreading  brackets  of  Polyporus  squamosus  are  of 
considerable  width,  so  that  they  stand  in  marked  contrast  with  those 
of  the  more  compact  and  extremely  rigid  fruit-bodies  of  Fovies 
igniarius,  &c.  The  dimensions  of  the  tubes  in  these  and  other 
species  seem  to  me,  at  least  to  a  certain  degree,  to  be  correlated  with 
the  nature  of  the  pileus  flesh. 

1  With  the  beam-of-light  method  (vide  infra,  Chap.  VII.)  it  was  observed  that 
when  the  tubes  of  Polystictus  hirsutus  were  tilted  to  an  angle  of  15°  from  the 
vertical,  there  was  a  marked  diminution  in  the  number  of  spores  liberated,  and 
that  with  a  tilt  of  30°  spore-liberation  almost  entirely  ceased. 

2  Specimens  which  had  been  gathered  and  kept  dry  for  six  months  began  to 
grow  on  their  undersides  when  they  were  placed  in  a  damp-chamber. 


CHAPTER    III 

THE  FUNCTIONS  OF  THE  STIPE  AND  OF  THE  PILEUS  FLESH— 
THE   GILL-CHAMBER 

THE  mechanics  of  the  stipes  of  the  more  complex  Hymenomycetes 
might  well  form  the  subject  of  an  interesting  and  a  detailed  investi- 
gation. A  few  remarks  may  here  be  made  in  this  connection  upon 
the  stipes  which  are  centrally  situated  beneath  radiate  pilei  in  the 
most  highly  developed  fruit-bodies.  The  stipe  can  support  the 
pileus  with  far  less  strain  in  a  centric  than  in  an  eccentric  position, 
and  it  seems  probable  that  this  mechanical  principle  has  been  one  of 
the  chief  factors  in  bringing  about  the  evolution  of  the  umbrella 
form  of  Agaric.  In  different  species  stipes  vary  much  in  length, 
thickness,  and  in  the  nature  and  disposition  of  the  materials  of  which 
they  are  composed  ;  but  no  doubt  there  is  always  a  correlation,  and 
often  a  close  one,  between  their  structure  and  the  work  which  they 
have  to  do  in  supporting  the  pileus  at  a  distance  from  the  ground, 
and  in  keeping  the  gills  in  exactly  vertical  planes. 

When  one  realises  how  very  important  it  is,  from  the  point  of 
view  of  spore-liberation,  that  the  planes  of  gills,  the  axes  of  hymenial 
tubes,  &c.,  should  be  kept  quite  motionless  in  a  vertical  position,  one 
cannot  be  surprised  to  find  that  the  mechanical  structure  of  the 
stipe  and  pileus  flesh  is  such  as  to  give  the  whole  fruit-body  a 
remarkable  amount  of  stability.  Were  the  gills  of  Agaricineae,  or 
the  hymenial  tubes  of  Polyporea?,  subjected  to  even  slight  continuous 
tilting  movements,  it  is  certain  that  a  great  proportion  of  the  spores 
could  never  be  liberated — for  after  discharge  from  their  basidia,  vast 
numbers  of  them  would  strike  and  adhere  to  the  hymenium.  In  the 
Mushroom,  for  example,  it  has  been  found  1  that  in  still  air  the  paths 
of  fall  of  the  spores  in  the  interlamellar  spaces  are  as  shown  in 
Fig.  12,  A.  When  the  planes  of  the  gills  are  tilted  1°  30',  the  spores 
1  Vide  infra,  Chap.  XVII. 


4o 


RESEARCHES   ON  FUNGI 


can  readily  escape  (B).  If  the  tilt  be  increased  to  2°  30',  the  critical 
angle  is  reached  (C) :  all  the  spores  can  still  make  their  way  out 
between  the  gills,  but  with  any  increase  in  the  tilt  some  of  them  fall 
upon  the  hymenium  and  adhere  there.  With  a  tilt  of  5°  half  the 
spores  are  lost  (D),  and  with  a  tilt  of  9°  30'  four-fifths  of  them  (E). 
The  gills  of  a  Mushroom  are  radially  disposed,  and  it  is  therefore 
evident  that,  if  a  Mushroom  is  tilted,  those  gills  with  their  planes 


FlG.  12.— The  effect  of  tilting  the  gills  of  Psalllota  campeslris.  Two  gills  are  shown 
in  cross  section.  The  arrows  in  the  interlamellar  space  indicate  the  paths  of 
the  spores  discharged  in  still  air.  A,  gills  in  the  normal  position.  In  B  the 
gills  are  tilted  1°  30'  from  the  vertical,  in  C  2°  30',  in  D  5°,  and  in  E  9°  20'. 

most  nearly  perpendicular  to  the  plane  of  tilt  will  suffer  most,  whilst 
those  with  their  planes  most  nearly  parallel  to  the  plane  of  tilt  will 
suffer  least.  The  exact  proportion  of  spores  lost  by  a  whole  Mush- 
room with  a  tilt  of  a  given  angle  would  be  somewhat  difficult  to 
calculate,  and  no  attempt  will  be  made  here  to  solve  this  problem. 
It  is  sufficiently  clear,  however,  that  when  the  pileus  of  one  of  the 
Agaricinese  is  tilted  only  a  few  degrees  from  its  normal  position,  its 
spore-liberating  efficiency  is  greatly  reduced.  In  this  connection,  it 
is  a  distinctly  significant  fact  that  all  hyrnenomycetous  fruit-bodies 


THE   FUNCTIONS   OF  THE   STIPE  41 

are  so  constructed  that  in  ordinary  weather  they  remain  quite 
motionless.  Those  with  the  longest  stipes,  e.g.  Coprinus  comatus, 
scarcely  sway  on  very  windy  days,  whilst  most  fruit-bodies  remain 
practically  unstirred  even  during  gales.  In  a  field,  the  stability  of  a 
Mushroom  may  be  contrasted  with  the  instability  of  a  neighbouring 
grass  stein;  but  we  must  recognise  that  the  peculiar  mechanical 
properties  of  both  Cryptogam  and  Phanerogam  are  equally  fraught 
with  a  beautiful  significance.  Each  plant  reacts  to  the  motion  of 
the  breeze  in  a  manner  most  suited  to  its  own  special  needs. 

Centric  stipes  are  usually  cylindrical.  In  some  spebies,  e.g. 
Russulae,  &c.,  the  cylinder  is  quite  solid,  although,  as  a  rule,  it  is 
firmest  toward  the  exterior ;  in  others,  it  has  a  narrow  central  core, 
stuffed  with  soft,  loosely  interlacing  hyphse,  or  left  quite  unfilled  as 
in  Amanita  phalloides  (Fig.  13)  or  the  Mushroom;  whilst  in  yet 
others,  of  which  Coprinus  coinatus  is  a  good  example,  it  assumes 
the  form  of  a  perfect  hollow  cylinder  with  a  comparatively  thin  wall 
(Plate  I.,  Fig.  1).  The  hollow  cylinder  has  the  same  significance  in 
Fungi,  in  Flowering  Plants,  and  in  structures  built  by  engineers. 
Where  it  is  employed,  advantage  is  taken  of  the  fact  that  with  a 
given  length  and  a  given  amount  of  material,  a  hollow  cylinder  is 
more  rigid  and  offers  more  resistance  to  bending  than  a  solid 
one. 

Where  the  pileus  is  large,  as  in  many  Russulse  and  Boleti,  the 
stipe  is  usually  thick,  solid,  and  so  rigid  or  tough  that  it  is  not  easily 
displaced ;  it  appears  to  be  constructed  as  if  to  resist  more  particu- 
larly any  downward  pressure  from  above,  arising  from  obstacles  met 
with  in  pushing  up  the  broad  pileus,  or  which  might  come  to  rest 
on  the  fruit-body  after  its  development.  On  the  other  hand,  there 
are  many  species  with  small  pilei  placed  on  long  stipes.  Here  the 
pileus  is  usually  conical  or  dome-shaped,  and  the  stipe  forms  a 
perfectly  hollow  cylinder  or  one  with  a  thin  firm  wall  and  a  very 
soft  core.  The  whole  fruit-body,  whilst  being  fairly  rigid,  is  much 
more  elastic  than  the  larger  ones  to  which  we  have  referred,  and 
seems  adapted  for  pushing  its  way  up  between  surrounding  grass 
stems,  &c.,  for  throwing  off  rain-water,  and  for  resisting  lateral 
pressure.  Illustrations  of  long,  hollow  stipes  may  be  found  in  the 
genera :  Mycena,  Galera,  Stropharia,  Coprinus,  &c.  Thin-stiped  fruit- 


42  RESEARCHES   ON   FUNGI 

bodies,  e.g.  those  of  Mycena  epipterygia,  have  a  distinct  advantage 
over  thick-stiped,  such  as  those  of  Russula  emetica,  in  that,  if  the 
fruit-body  should  be  even  considerably  displaced  by  any  accident, 
it  can  quickly  be  set  once  more  with  the  gills  in  vertical  planes  by 
means  of  a  suitable  geotropic  curvature  of  the  stipe.  With  Russuhe, 
Psalliotse,  &c.,  owing  to  the  thickness  of  the  stipes,  this  is  impossible 
when  the  pilei  have  become  outstretched.  In  these  cases,  the  gills 
themselves  react  to  the  stimulus  of  gravity,  and  after  a  slight  dis- 
placement of  the  fruit-body,  quickly  readjust  themselves  so  as  to 
come  to  lie  in  vertical  planes  once  more ;  but  when  the  displacement 
is  considerable,  this  remedy  becomes  of  very  little  avail.  In  species 
of  Galera,  Mycena,  &c.,  the  structure  of  the  stipe  is  such  as  to  remind 
one  of  the  hollow  peduncle  which  supports  the  capitulum  of  a 
Dandelion  or  the  pith-filled  one  of  a  Chrysanthemum.  It  is  clear 
that  for  the  stipes  of  Agaricineae  we  have  a  series  of  variations 
in  the  cylindrical  form  comparable  with  that  found  in  the  stems  of 
Phanerogams  and  bearing  a  similar  interpretation. 

A  certain  amount  of  rigidity  is  given  to  many  stipes,  not  merely 
by  their  cylindrical  form,  but  also  by  longitudinal  tensions  set  up 
in  the  layers  of  hyphse  of  which  they  are  composed.  The  existence 
of  these  tensions  can  easily  be  proved  by  partially  bisecting  or 
quadrisecting  the  stipes  concerned,  e.g.  those  of  Coprinus  comatus, 
Mycense,  &c.,  in  a  longitudinal  direction  from  below  upwards,  with 
a  knife.  The  halves  or  quarters  so  produced  bend  outwards  and 
resist  attempts  to  replace  them  in  their  original  positions  (Fig.  13). 
It  is  well  known  that  similar  tensions  occur  in  the  young  stems 
of  the  Higher  Plants. 

The  foregoing  remarks  tend  to  show  that  stipes  in  general  are 
well  adapted  to  give  the  basidia  the  best  possible  chance  of  dis- 
charging their  spores,  so  that  they  may  freely  escape  from  the 
fruit-body.  There  can  be  no  doubt  that  the  pileus  flesh  is  adapted 
to  the  same  end.  Its  function  is  not  merely  to  support  the  weight 
of  the  gills  or  hy menial  tubes,  but  to  hold  them  fixed  in  one 
particular  position.  As  one  might  expect  from  a  very  simple 
mechanical  consideration,  the  pileus  flesh  is  always  thickest  toward 
the  centre  and  thins  out  rapidly  in  the  peripheral  direction.  Its 
exact  form  and  the  materials  of  which  it  is  composed  vary  much 


THE   FUNCTIONS   OF  THE   STIPE 


43 


in  different  species,  so  that  its  peculiar  mechanical  needs  are 
doubtless  met  in  slightly  different  ways. 

In  certain  species  of  Polyporus  which  have  central  stipes — 
P.  pisochapani,  P.  rugosus,  P.  lepideus,  and  P.  floccopus — there 
is  present,  according  to  Massee,1  a  highly  developed  mechanical 
sheath  to  both  pileus  and  stipe.  The  occurrence  of  this  structure 
points  to  an  unusually  marked  division  of  labour  between  the 
nutritive  and  supporting  parts  of  the  fruit-bodies. 

In  Coprinus  coinatus  (Plate  I.,  Fig.  1)  the  pileus  has  the  form  of 
a  bell,  and  its  centre 

C 


of  gravity  is  situated 
at  soine  distance  be- 
low its  place  of  at- 
tachment to  the  stipe. 
It  is  thus  in  a  state 
of  stable  equilibrium, 
and  doubtless,  in  cor- 
relation with  this 
mechanical  fact,  it 
happens  that  the  pi- 
leus and  stipe  are  very 
loosely  attached  to- 
gether. If  one  slightly 
tilts  the  stipe  of  a 
fruit-body  which  has 
just  opened,  the  pi- 
leus refuses  to  become 


FIG.  13. — Amanita  phalloides  (volva  removed).  A,  young 
fruit-body.  B,  mature  fruit-body.  The  stipe  has 
been  quadrisected  and  the  tensions  in  it  have  caused 
the  four  parts  to  separate.  C,  cross-section  of  a  stipe. 
All  |  natural  size. 


tilted  too,  but  instead  remains  in  its  optimum  position.  High 
winds  sometimes  cause  the  pileus  to  swing  slightly  about  the  fixed 
stipe.  However,  few  or  possibly  none  of  the  spores  would  thereby 
be  prevented  from  escaping  from  the  fruit-body,  owing  to  the 
peculiar  manner  in  which  they  are  liberated.2 

Among  the  most  beautiful  Agarics  in  nature  are  the  so-called 
Parasol   or   Umbrella  Fungi — Lepiota  procera  and  L.   rachodes — 

1  G.  Massee,  "  On  the  Differentiation  of  Tissues  in  Fungi,"  Journ.  Roy.  Micr. 
Soc.,  1887,  p.  205. 

»  Vide  infra,  Chap.  XIX. 


44 


RESEARCHES   ON  FUNGI 


which,  owing  to  their  large  size  and  striking  form,  attract  general 
attention  as  they  come  up  in  open  woods  (Fig.  14).  The  pilei 
consist  of  broad  plates  which  are  often  as  much  as  20  cm.  in 
diameter  and  raised  25  cm.  above  the  ground.  The  place  of 
attachment  of  the  stipe  to  the  pileus  flesh  is  very  high,  so  that 
it  is  evident  that  it  must  be  situated  1-2  cm.  above  the  centre 

of  gravity  of  the  whole  pileus  in 
large  fruit-bodies  (Fig.  15).  The 
stipe  can  easily  be  pulled  out 
from  the  pileus,  and  after  its 
removal  one  may  observe  that  it 
has  a  flattened  top.  The  free 
pileus  can  again  be  set  on  the 
upright  stipe.  If,  when  this  has 
been  done,  one  tilts  the  pileus 
by  pressing  down  one  side  of 
it  with  the  finger  and  then  lets 
it  go,  it  swings  back  into  its 
original  horizontal  position.  This 
could  not  happen  if  the  centre 
of  gravity  of  the  pileus  were  in 
any  other  situation  than  that  of 
stable  equilibrium.  Whilst  a 
fruit-body  is  growing  in  nature, 
so  far  as  I  have  observed,  the 
pileus  is  fairly  firmly  fixed 
upon  the  stipe,  and  does  not 
swing  appreciably  about  its  place 
of  attachment  during  winds. 
However,  to  what  extent  the  peculiar  position  of  its  centre  of 
gravity  enables  it  to  take  up  and  maintain  its  most  stable  position 
during  expansion,  still  remains  to  be  investigated. 

The  oldest  function  of  the  centric  stipe,  from  the  phylogenetic 
standpoint,  is  undoubtedly  that  of  providing  a  free  space  between  the 
pileus  and  the  ground,  so  that  the  falling  spores  may  be  carried  off 
by  lateral  movements  of  the  air.  A  space  of  this  kind  is  already 
present  in  such  primitive  fruit-bodies  as  those  of  Craterellus  cornu- 


FlG.  14. — Lepiota procera — the  Parasol  Fun- 
gus. Fruit-body  growing  among  grass. 
Photographed  at  Sutton  Park,  War- 
wickshire, by  J.  E.  Titley.  |  natural 
size. 


THE   GILL-CHAMBER  45 

copioides,  one  of  the  Thelephoreoe,  in  which  the  hymenium  is 
smooth  and  not  yet  produced  into  tubes,  teeth,  or  gills.  The 
length  of  the  stipe  in  a  few  very  tiny  fruit-bodies  is  not 
much  more  than  a  single  centimetre,  but  in  general  it  varies 
from  5-12  cm.  In  different  species  it  appears  to  bear  some  rela- 
tionship to  the  size  of  the  pileus  and  the  usual  nature  of  the 
environment.  In  a  single  species  the  stipes  of  individual  fruit- 
bodies  are  often  longest  when  development  has  taken  place  in 
badly  lighted  places.  The  power  of  adjustment  in  response  to 
conditions  of  light  doubtless  finds  its  significance  in  the  advantage 
gained  from  raising  up  the  pileus  above  surrounding  obstacles. 
In  most  species  the  stipe  does  not  elongate  when  once  the  gills 
have  become  outstretched,  but  in  Coprinus  comatus  it  goes  on 


FlG.  15- — Lepiota  procera.     Section  showing  mode  of  attachment  of  the  pileus 
to  the  stipe.     £  natural  size. 

lengthening  during  the  whole  period  of  spore-discharge,  so  that 
at  the  end  it  is  often  30  cm.  long.  A  good  explanation  can  be 
found  for  this  exception  to  the  general  rule,  but  it  will  be  more 
conveniently  dealt  with  in  Chapter  XIX.,  where  the  Coprinus  type 
of  fruit-body  is  described  in  detail. 

In  resupinate,  dimidiate,  and  most  fruit-bodies  with  centric 
stipes,  the  gills  are  exposed  from  their  earliest  appearance.  Guided 
by  this  fact,  we  may  regard  the  formation  of  a  distinct  gill-chamber, 
such  as  occurs  in  the  genus  Amanita,  Psalliota,  &c.  (Fig.  19), 
as  one  of  the  later  developments  in  the  evolution  of  Agarics. 
The  significance  of  this  structure  is  probably  to  be  found  in  the 
advantage  derived  from  protecting  the  gills  from  insects,  parasitic 
fungi,  and  other  enemies  until  the  last  possible  moment,  when 
their  expansion  and  free  exposure  to  the  air,  for  the  purpose  of 


46  RESEARCHES   ON  FUNGI 

liberating  spores,  becomes  absolutely  necessary.  Some  Mushrooms 
which  were  grown  for  my  purposes  on  a  bed  of  horse  manure, 
whilst  still  shedding  spores,  were  found  to  have  their  gills  infested 
with  tiny  animals,  possibly  Acarineae.  These,  when  running  about, 
doubtless  displaced  a  great  number  of  spores,  and  probably  also 
used  many  of  them  as  food.  The  extended  velum  partiale  must 
be  an  admirable  means  of  keeping  such  creatures  as  these  away 
from  the  young  gills,  until,  by  its  rending  during  the  rapid 
expansion  of  the  pileus,  the  gill-chamber  is  broken  open.  A  part 
of  the  velum  is  often  left  on  the  stipe  in  the  form  of  a  more  or 
less  pronounced  ring,  as  in  Coprinus  comatus  (Fig.  70,  p.  199), 
whilst  in  Amanita  muscaria  and  allied  species  (Fig.  75,  p.  212), 
it  hangs  down  in  the  form  of  a  curtain.  In  the  latter  instance, 
its  position  is  such  that  it  does  not  seriously  interfere  with  the 
falling  spores  as  they  are  being  carried  oft'  by  air  movements. 
It  is  the  extreme  thinness  and  flexibility  of  the  velum  which 
permits  of  its  falling  into  the  most  unobstructive  position  when 
it  can  no  longer  be  of  any  service  to  the  fruit-body. 


CHAPTER   IV 

ADJUSTMENTS  OF  FRUIT-BODIES  IN  THE  INTERESTS  OF  SPORE- 
LIBERATION—  LENTIN US  LEPIDEUS,  PSALLIOTA  CAMPESTRIS, 
POLYPORUS  SQUAMOSUS,  COPR1XUS  PLICATILIS,  COPRINUS 
NIVEUS,  A^Tt  COPRINUS  PLICATILOIDES— REACTIONS  OF  FRUIT- 
BODIES  TO  LIGHT  AND  GRAVITY— THE  PROBLEM  OF-  PILEUS 
ECCENTRICITY— GEOTROPIC  SWINGING— RUDIMENTARY  FRUIT- 
BODIES 

IN  order  to  obtain  a  more  precise  knowledge  of  the  means 
whereby,  and  the  extent  to  which,  a  fruit-body  is  able  to  adjust 
itself  so  as  to  bring  its  hymenium  into  the  optimum  position 
for  spore  -  liberation,  experiments  were  made  upon  Lentinus 
lepideus,  Psalliota  campestris,  Polyporus  squamosus,  Coprinus 
plicatilis,  C.  niveus,  and  C.  plicatiloides,  the  sporophores  of  which 
differ  considerably  from  one  another.  The  first  two  species  belong 
to  the  Agaricineae  but  occupy  different  habitats.  Lentinus  lepideus 
is  saprophytic  on  wood  and  often  produces  its  fruit -bodies  on 
surfaces  which  are  nearly  or  quite  vertical,  such  as  those  of  logs 
and  stumps ;  whilst,  on  the  other  hand,  as  every  one  has  observed, 
the  Mushroom  comes  up  in  more  or  less  horizontal  pastures, 
Polyporus  squamosus  is  a  wound-parasite  on  trees,  and  is  most 
frequently  found  attached  laterally  to  tree  trunks  or  thick  branches. 
Coprinus  plicatilis  belongs  to  a  highly  specialised  genus.  Its 
fruit-bodies  are  of  small  size  and  come  up  in  short  grass.  C.  niveus 
and  C.  plicatiloides  are  found  on  horse  dung. 

Lentinus  lepideus.  —  The  fruit-bodies  developed  on  rotting 
paving  blocks  removed  from  the  streets  of  the  city  of  Birming- 
ham. Their  reactions  to  external  stimuli  have  already  been 
described  in  detail  in  a  special  paper.1  It  will  therefore  only 
be  necessary  here  to  state  those  results  of  experiment  which 
bear  upon  our  problem. 

1  Buller,  "  The  Reactions  of  the  Fruit-bodies  of  Lentinus  lepidens  to  External 
Stimuli,"  Ann.  of  Bot.,  1905,  vol.  xix.  pp.  427-438. 


48 


RESEARCHES   ON  FUNGI 


A  fruit-body  begins  its  existence  in  light  or  darkness  as  a 
tiny  papilla,  directed  at  any  angle  to  the  substratum,  but  pro- 
jecting more  or  less  vertically  from  the  surface  of  the  stromatous 
layer  on  which  it  is  produced  (Fig.  16,  A).  If  developed  in  the 
dark  the  papilla  grows  out  into  a  long  finger-like  stipe,  which 
is  perfectly  indifferent  to  geotropic  stimuli.  In  the  course  of 
six  weeks  the  stipe  may  attain  a  length  of  15  cm.  without  showing 
the  least  trace  of  a  pileus  (D),  and  sometimes  it  may  become 
branched  (C).  In  weak  light  it  is  positively  heliotropic  and 


FlG.  16. — The  forms  of  Lentinus  lepideus.  A,  diagram  showing  the  beginnings 
of  fruit-bodies  as  conical  processes,  c,  arising  on  a  stroma,  s,  developed  on 
wood.  B,  section  of  a  normal  fruit-body  grown  in  light.  C,  sterile  and 
branched  fruit-body  found  growing  in  darkness.  D,  sterile  and  finger-like 
fruit-body  after  three  weeks'  growth  in  darkness.  E,  f-ection  of  a  fruit- 
body  with  eccentric  pileus.  F,  G,  H,  and  I,  branched  and  feebly- developed 
fruit-bodies  grown  in  weak  light.  All  J  natural  size. 

thus  reacts  to  this  stimulus  as  if  attempting  to  bring  its  free  end 
into  the  best  illuminated  position.  When  the  tip  of  the  stipe 
is  acted  upon  by  light  of  sufficient  intensity,  it  flattens  and 
expands  in  a  symmetrical  manner,  and  becomes  converted  into 
a  pileus.  As  soon  as  the  development  of  this  structure  has  been 
initiated,  a  remarkable  change  takes  place  in  the  physiological 
properties  of  the  stipe.  Whilst  still  barren,  this  was  absolutely 
without  response  to  geotropic  stimuli  but  was  positively  heliotropic ; 
it  now  becomes  strongly  negatively  geotropic  and  entirely  loses 
its  power  of  reacting  to  light.  The  rapidly  developing  pileus 


ADJUSTMENTS   OF   FRUIT-BODIES  49 

thus  comes  to  have  its  axis  turned  upwards  into  a  vertical 
position.  The  gills  at  the  beginning  of  their  development  simply 
grow  outwards  in  directions  which  are  perpendicular  to  the  under 
surface  of  the  pileus.  Their  only  reaction  to  external  stimuli 
appears  to  be  that  of  positive  geotropism,  which  comes  into  play 
as  soon  as  they  have  attained  a  certain  breadth. 

The  turning  movement  which  is  necessary  in  order  to  bring 
the  planes  of  the  gills  into  exactly  vertical  positions,  in  the  main 
is  accomplished  by  the  stipe,  but  for  its  completion  the  sensitive 
gills  are  themselves  alone  responsible.  In  the  work  of  securing 
a  proper  orientation  for  the  hymenial  surfaces,  the  stipe  acts  as 
a  c6arse  adjustment  and  each  gill  as  a  fine  adjustment.  In 
their  nature  and  successive  action  these  two  adjustments  are 
strictly  analogous  to  those  which  are  employed  in  focussing  the 
high  power  of  a  microscope. 

The  reactions  to  external  stimuli  which  have  just  been  detailed 
are  such  that: — 

(1)  The  barren  stipe  grows  in  a  manner  suited  to  find  a  way 
to  the  open  air. 

(2)  The  pileus  is  never  developed  in  any  space  which  is  shut 
out  from  daylight,  and  therefore  of  such  a  character  that,  if  spores 
were  liberated  into  it,  they  could  not  be  properly  disseminated. 

(3)  As  soon  as  a  pileus  has  begun  its  development,  its  hymenium 
can  readily   be   placed   in    the    optimum    position    by   a    suitable 
curvature   of  the   stipe   combined  with   a  subsequent   adjustment 
of  the  gills. 

The  fruit-bodies  of  Lentinus  lepideus,  when  growing  out  from 
the  side  of  a  piece  of  wood,  to  some  extent  exhibit  the  phenomenon 
of  eccentricity  of  development.  In  extreme  cases,  under  cultural 
conditions,  the  pileus  flesh  may  become  quite  unilateral  (Fig.  16,  E). 
I  have  shown  that  this  is  due  to  a  morphogenic  stimulus  of 
gravity  acting  upon  a  pileus  developing  upon  an  oblique  stipe. 
There  can  be  no  doubt  that  the  reaction  is  advantageous  in  that 
it  permits  of  the  fruit-body  developing  the  chief  part  of  its  spore- 
producing  surface  in  a  situation  where  the  spores  will  run  the 
least  risk  of  catching  upon  the  stipe  whilst  making  their  escape. 
1  Loc.  tit.,  p.  431. 


50  RESEARCHES   ON   FUNGI 

We  shall  return  to  the  problem  of  pileus  eccentricity  in  con- 
nection with  Polyporus  squamosus.  It  may,  however,  here  be 
pointed  out  that  the  power  of  response  to  the  inorphogenic 
stimulus  of  gravity  varies  much  in  different  species  of  Hymeno- 
mycetes.  In  Psalliota  campestris,  in  Coprinus,  and  probably 
quite  generally  in  ground  Agaricineae,  it  is  not  present  at  all; 
in  Lentinus  lepideus  and  certain  other  comparatively  long-stiped 
Agaricinese  it  is  slightly  developed ;  whilst  in  the  relatively  short- 
stiped  Pleurotus  ostreatus  and  Polyporus  squamosus,  and  in  the 
stipeless,  bracket-shaped  fruit-bodies  growing  on  trees  it  is  very 
marked. 

From  the  above  it  seems  clear  that  the  fruit-bodies  of  Lentinus 
lepideus  possess  in  a  high  degree  the  power  of  adjusting  themselves 
in  a  manner  suited  to  their  environment.  In  nature  it  sometimes 
happens,  as  I  have  once  observed,  that  a  fruit-body  begins  its 
development  on  the  underside  of  a  log  or  other  mass  of  wood. 
Even  then  it  can  still  succeed  in  placing  its  gills  in  their  optimum 
position. 

Psalliota  campestris. — Mushrooms  were  first  of  all  studied  as 
they  came  up  under  natural  conditions  in  a  large  pasture.  The 
actual  amount  of  curvature  which  the  stipes  of  the  fruit-bodies 
investigated  had  undergone  in  extreme  cases  during  development 
may  be  gathered  from  Fig.  17,  in  which  some  field  sketches  have 
been  reproduced.  The  curvatures  had  been  sufficient  to  place 
the  planes  of  all  the  pilei  in  a  horizontal  position.  However,  in 
older  Mushrooms,  it  was  found  that  the  stipe  only  acts  as  a  coarse 
adjustment  for  the  gills.  The  latter  are  very  thin,  fairly  deep, 
and  closely  packed;  and  the  fine  adjustment  of  their  planes  in 
exactly  vertical  directions  can  only  be  effected  by  their  own 
delicate  reactions  to  the  stimulus  of  gravity. 

When  an  accident  happens  to  a  mature  Mushroom  so  that  it 
becomes  tilted,  as  is  often  the  case  in  pastures  where  horses  and 
cattle  are  browsing,  the  stipe  and  pileus  remain  fixed  in  their 
new  positions.  However,  the  gills  are  still  in  a  most  sensitive 
condition  and  quickly  respond  to  the  stimulus  of  gravity.  Each 
gill  grows  faster  on  its  upper  side  than  on  its  lower  side  and 
thus  gradually  curves  downwards,  so  that  a  large  part  of  it  comes 


ADJUSTMENTS   OF   FRUIT-BODIES  51 

to  look  once  more  directly  toward  the  earth.  The  rate  and  the 
amount  of  the  reaction  depend  upon  various  conditions,  particularly 
on  the  stage  of  development  of  the  fruit-body  and  the  amount 
of  the  tilt.  The  younger  the  gills  and  the  smaller  the  tilt,  the 
quicker  and  more  complete  is  the  readjustment  hi  a  vertical 
plane.  An  expanded  Mushroom  was  placed  so  that  the  plane 
of  the  pileus  was  vertical,  and  those  gills  which  most  nearly 
occupied  horizontal  planes  were  then  looked  at  edgewise  with  a 
horizontal  microscope.  The  reaction  to  the  stimulus  of  gravity 


FlG.  17. — Psattiota  campestris.  Adjustment  of  the  pileus  by  geotropic  curvature 
of  the  stipe.  A,  Mushroom  grown  upside  down  in  a  pot.  B,  two  Mushrooms 
grown  laterally  in  a  pot.  To  the  left,  five  Mushrooms  gathered  and  sketched 
in  a  field.  All  \  natural  size. 

was  found  to  begin  in  about  an  hour  after  the  fruit-body  had 
been  gathered  and  tilted.  After  two  hours  the  downward  cur- 
vature of  the  free  edge  of  the  gills  was  marked  and  could  be 
detected  with  the  naked  eye. 

When  the  plane  of  a  Mushroom  pileus  has  not  been  tilted  up 
to  an  angle  of  more  than  about  30°,  all  the  gills  can  adjust  them- 
selves again  so  as  to  take  up  vertical  positions.  This  is  permitted 
by  the  provision  of  a  sufficient  margin  of  safety  in  their  spacial 
arrangement.1  When,  however,  the  tilt  exceeds  a  certain  amount, 
i  Cf.  Chap.  II. 


52  RESEARCHES   ON   FUNGI 

some  of  the  gills  crowd  one  another  unduly,  and  only  a  few  of  the 
highest  have  room  to  turn  so  as  to  give  themselves  the  chance 
of  successfully  liberating  spores.  Some  Mushrooms  which  had 
undergone  symmetrical  development  on  an  artificial  bed  were 
picked  and  fixed  so  that  the  planes  of  their  pilei  were  set  in  a 
vertical  direction.  Previous  to  the  experiment  the  gills  looked 
downwards  in  the  most  perfect  manner,  and  the  undersides  of  the 
pilei  presented  the  appearance  shown  in  Plate  IV.,  Fig.  25.  After 
being  placed  in  their  new  positions  the  gills  soon  reacted  to  the 
stimulus  of  gravity  and  attempted  to  make  the  usual  adjustment. 
However,  owing  to  the  fruit-bodies  having  been  tilted  through  an 
angle  of  90°,  this  could  not  be  successfully  accomplished.  A  photo- 
graph of  the  pilei,  as  they  appeared  at  the  end  of  the  experiment, 
is  reproduced  in  Fig.  18.  It  will  be  seen  therefrom  that  only  a 
very  few  gills  at  the  top  of  each  pileus  remained  separated  from  one 
another.  These  liberated  a  few  spores,  which  settled  on  the  upper 
sides  of  the  extreme  tops  of  the  stipes.  The  rest  of  the  gills  had 
become  so  crowded  that  they  covered  one  another  up.  It  is  not 
surprising,  therefore,  that  practically  no  spore-deposit  accumulated 
on  paper  placed  immediately  below  the  pilei. 

It  seemed  of  interest  to  find  out  to  what  extent  the  stipe  of  a 
Mushroom  is  capable  of  undergoing  curvature  when  the  pileus 
has  been  placed  by  artificial  means  hi  a  very  unfavourable  position. 
Accordingly,  some  Mushroom  spawn  was  planted  in  large  pots 
containing  horse  manure  covered  with  soil.  After  a  few  weeks 
fruit-bodies  duly  made  their  appearance,  but  before  they  had 
attained  the  size  of  peas  their  position  was  altered.  Some  of 
the  pots  were  suspended  upside  down  and  others  fixed  horizontally 
on  their  sides.  The  soil  was  kept  in  place  by  the  careful  use  of  sticks 
and  wire  netting.  Under  these  conditions  the  fruit-bodies  continued 
to  grow,  and  the  stipe  of  each  made  an  attempt  to  place  the  pileus 
in  the  usual  position.  Where  the  pots  had  been  inverted  the 
attempt  proved  to  be  almost  a  complete  failure  (Fig.  17,  A),  but 
where  the  fruit-bodies  grew  out  from  the  soil  laterally  it  was 
attended  with  a  large  measure  of  success  (Fig.  17,  B).  Had  the 
fruit-bodies  in  the  latter  instance  been  larger  and  of  more  vigorous 
growth,  probably  the  success  would  have  been  somewhat  greater. 


ADJUSTMENTS   OF  FRUIT-BODIES 


53 


It  is  evident,  however,  from  these  experiments  that  the  stipe  of  a 
Mushroom  has  but  small  powers  of  making  geotropic  curvatures 


FlG.  18. — Psalliota  campestris.  Geotropic  reaction  of  the  gills.  The  pilei  were 
fixed  with  their  planes  in  a  vertical  position.  In  the  course  of  about 
twenty-four  hours  the  gills,  in  attempting  to  readjust  themselves  in  vertical 
planes,  took  up  the  positions  shown  in  the  photograph.  Natural  size. 

when  compared  with  that  of  Lentiniis  lepideus,  or  those  of  species 
of  Mycena,  Psathyrella,  and  Coprinus,  &c. ;  but  owing  to  the  fact 


54  RESEARCHES   ON   FUNGI 

that  the  pastures  where  Mushrooms  grow  are  always  more  or  less 
horizontally  disposed,  large  curvatures  are  quite  unnecessary.  As 
a  matter  of  fact,  in  extreme  cases  in  the  field,  the  needs  of  the 
pileus  can  be  fully  met  when  the  stipe  bends  through  an  angle  of 
only  about  45°  (Fig.  17,  to  the  left). 

It  seems  probable  that  the  position  of  the  pileus  at  its  origin  is 
simply  determined  by  the  direction  of  the  stromatous  strand,  upon 
the  end  of  which  the  fruit-body  concerned  comes  to  be  developed. 
However  this  may  be,  there  can  be  no  doubt  that,  as  soon  as  the 
pileus  and  stipe  have  become  differentiated,  the  direction  of  further 
growth  of  the  fruit-body  (excluding  mechanical  resistance  offered 
by  grass,  &c.)  is  entirely  controlled  by  the  stimulus  of  gravity  ; 
and  it  is  to  this,  and  to  this  alone,  that  a  Mushroom  owes  its 
characteristic  position  in  the  field.  The  stipe,  when  not  yet  2  cm. 
long,  becomes  negatively  geotropic  in  a  zone  just  below  the  pileus 
flesh;  whilst  subsequently  the  gills,  after  partial  development, 
place  themselves  very  exactly  in  vertical  planes  by  growing  toward 
the  earth's  centre. 

When  Mushrooms  come  up  in  fields  the  mechanical  resistance 
offered  by  the  herbage  often  hinders  the  stipe,  when  young,  from 
bending  straight  upwards.  As  the  stipe  gets  longer  and  longer 
the  pileus  becomes  pushed  more  and  more  into  freedom.  When 
this  has  been  attained  the  stipe  simply  grows  directly  upwards, 
but  evidence  of  its  early  struggle  is  still  left  in  its  curved  or  zigzag 
form  (cf.  Fig.  17). 

Werner  Magnus1  observed  that  when  a  Mushroom  comes  up 
on  a  sloping  bed  so  that  it  catches  in  the  manure  and  has  to  push 
up  against  it,  the  stipe  becomes  unusually  long  whilst  the  pileus 
remains  small.  He  also  found  that  when  a  young  pileus  is  pre- 
vented from  expanding  by  means  of  a  ring  of  gypsum,  its  growth 
practically  ceases  and  the  stipe  attains  a  quite  abnormal  length. 
This  peculiar  correlation  in  growth  between  pileus  and  stipe  in 
nature  probably  sometimes  helps  to  determine  the  form  of  Mush- 
rooms, for  these  occasionally  are  to  be  found  pushing  their  way 

1  W.  Magnus,  "Ueber  die  Formbildung  der  Hutpilze,"  Archiv  fur  Biontologie, 
Bd.  I.,  1906,  p.  104. 


ADJUSTMENTS   OF  FRUIT-BODIES  55 

up  against  soil,  grass,  or  dung,  &c.,  in  such  a  manner  that  con- 
siderable resistance  is  ottered  to  the  free  expansion  of  the  pilei. 
The  chief  effect  of  an  unusual  lengthening  of  the  stipe  upon  a 
fruit-body  as  a  spore-producing  organ,  consists  in  increasing  the 
chances  of  the  pileus  being  raised  to  such  a  height  that  it  becomes 
freed  from  obstacles  and  can  successfully  liberate  its  spores. 

Light  gives  rise  in  a  Mushroom  neither  to  a  heliotropic  nor 
to  a  morphogenic  reaction.  I  have  been  unable  to  detect  any 
heliotropic  curvatures  of  the  stipes  of  fruit-bodies  grown  on  artificial 
beds  of  horse  manure,  and  a  special  experiment  with  wild  Mush- 
rooms also  gave  negative  results.  Eight  pieces  of  turf,  containing 
Mushrooms  in  an  early  button  stage  of  development,  were  taken 
up  from  a  field  and  placed  in  a  room  in  such  a  way  that  the 
buttons  were  well  lighted  on  one  side  and  in  strong  shadow  upon 
the  other.  However,  the  stipes  grew  up  vertically  and  exhibited 
no  signs  of  bending  toward  the  source  of  light.  That  Mushrooms 
do  not  give  a  morphogenic  reaction  to  illumination  may  be  deduced 
from  the  fact  that  they  develop  in  form  equally  well  in  a  perfectly 
dark  cellar  and  in  a  sunlit  field. 

The  development  of  the  fruit-bodies  of  Lentinus  lepideus  is 
controlled  by  light  and  gravity  in  succession,  whilst  those  of 
Psalliota  campestris  react  to  gravity  alone.  This  difference 
seems  to  me  to  be  connected  with  the  diversity  in  the  habitats 
of  the  two  species.  Lentinus  lepideus  is  a  wood  fungus.  The 
orientation  of  the  surface  of  its  substratum  is  indefinite,  and  may 
be  most  varied  in  respect  to  the  fruit-bodies.  Response  to  both 
light  and  gravity  under  these  circumstances  is,  as  already  explained, 
of  distinct  advantage.  On  the  other  hand,  Psalliota  campestris  is 
a  ground  fungus.  The  orientation  of  its  substratum  is  in  so  far 
definite  that  the  surface  is  on  the  average  horizontal.  This  being 
so,  when  a  fruit-body  has  ouce  begun  to  form  on  the  surface  of 
the  ground,  a  negative  geotropic  reaction  alone  is  sufficient  to 
enable  the  stipe  to  raise  the  pileus  and  bring  it  into  the  optimum 
position.  Hence,  we  find  that  the  development  of  the  Mushroom 
is  regulated  from  without  simply  by  the  stimulus  of  gravity.  No 
advantage  would  be  gained  by  sensitiveness  to  light,  and  indifference 
towards  it  is  therefore  easily  understood. 


56  RESEARCHES   ON   FUNGI 

The  adjustments  by  which  the  hy menial  surfaces  are  placed  in 
the  optimum  position  for  spore-liberation  in  the  Mushroom  are  no 
less  than  four  in  number,  and  may  be  summed  up  as  follows : 
(1)  Turning  the  pileus  into  an  erect  position  by  an  upward 
curvature  of  the  stipe ;  (2)  raising  the  pileus  several  centimetres 
above  the  ground  by  growth  in  length  of  the  stipe ;  (3)  placing 
the  gills  with  their  long  axes  horizontal  by  an  expansion  of  the 
pileus  (Fig.  19);  and  (4)  setting  the  planes  of  the  gills  in  hori- 


FlG.  19.  — Psalliota  arvensis.  a-d,  sections  of  four  fruit-bodies  showing  suc- 
cessive stages  in  the  raising  of  the  gills  into  a  horizontal  position  by  the 
expansion  of  the  pileus.  At  a  the  gills  are  still  enclosed  in  the  large  gill 
chamber.  All  £  natural  size. 

zontal  positions  by  the  turning  of  the  gills  themselves  about  their 
directions  of  attachment  to  the  pileus  flesh.  Whilst  the  erection  of 
the  pileus  and  the  turning  of  the  gills — coarse  and  fine  adjustments 
respectively — are  controlled  by  the  external  stimulus  of  gravity,  the 
raising  of  the  pileus  and  its  expansion  are,  doubtless,  due  to  internal 
developmental  forces  alone.  Proof  of  the  latter  statement  seems  to 
be  afforded  by  the  fact  that  Mushrooms  can  elongate  their  stipes 
and  expand  their  pilei  when  growing  upside  down  in  the  dark 
(cf.  Fig.  17,  A). 

Polyporus   squamosus.1 — P.   squamosus,  the  Great  Scaly  Poly- 

1  Cf.   Buller,    "The    Biology    of    Polyporus    sqtiamosus,  a    Timber-destroying 
Fungus,"  Journ.  of  Economic  Biology,  1906,  vol.  i.  pp.  101-138. 


ADJUSTMENTS   OF  FRUIT-BODIES  57 

porus  or  Saddle-Back  Fungus,  is  one  of  the  best  known  European 
species  of  tree-destroying  fungi,  and  it  is  also  found  in  the  United 
States  and  Canada.  Its  large  ochraceous  fruit-bodies,  checkered 
with  brown  scales  above,  are  frequently  to  be  seen  projecting  as 
brackets,  either  singly  or  in  groups,  from  trunks  and  branches  of 
living  trees  in  woods,  parks,  and  gardens  (Figs.  1  and  4-7,  pp.  8, 
28,  29,  32,  and  33 ;  also  Plate  V.). 

For  the  purpose  of  studying  the  development  of  the  fruit-bodies 
under  special  conditions,  several  logs  which  had  been  half  destroyed 
by  the  mycelium  were  procured  and  removed  to  an  experimental 
greenhouse.  As  this  was  conveniently  provided  with  a  dark-room, 
it  was  possible  to  grow  the  sporophores  in  total  darkness  as  well 
as  in  ordinary  daylight. 

When  the  mycelium  of  the  fungus  is  about  to  produce  fruit- 
bodies,  it  grows  out  on  to  the  surface  of  the  tree  trunk  or  branch, 
usually  at  a  place  where  the  bark  has  been  removed.  It  there 
forms  a  more  or  less  rounded,  but  somewhat  irregular,  stromatous 
knob  of  firm  consistency  (Plate  V.,  Fig.  36).  When  this  knob 
has  reached  a  certain  size  and  is  less  than  twenty-four  hours  old, 
one,  or  usually  several,  bluntly  conical  processes  arise  upon  it, 
grow  straight  outwards  from  its  surface,  and  thus  come  to  point 
in  different  directions  in  space  (Fig.  21,  A;  Plate  V.,  Figs.  31 
and  37).  The  development  up  to  this  point  takes  place  about 
equally  well  under  all  conditions  of  light.  It  is  noticeable,  however, 
that  the  knobs  produced  in  darkness  are  quite  white  and  smooth, 
whereas  those  arising  in  full  daylight  are  somewhat  brown  and 
scaly. 

When  fruit-bodies  develop  entirely  in  the  dark,  the  conical 
processes  on  the  stromatous  knobs  grow  outwards  into  long  sterile, 
finger-like  columns  which  are  usually  curved  or  twisted,  frequently 
flattened  toward  their  ends,  and  in  many  cases  branched.  In  the 
course  of  three  weeks,  vigorous  fruit-bodies  may  attain  a  length 
of  15  cm.  and  come  to  resemble  a  stag's  horn  (Fig.  20).  The 
branches  grow  at  their  apices  only ;  their  ends  are  pure  white, 
whilst  the  older  parts  become  deep  black,  like  the  base  of  the 
stipes  in  fruit-bodies  developed  in  daylight. 

The  horn-like  processes  just  described  appear  to  be  unaffected, 


58  RESEARCHES   ON   FUNGI 

in  respect  to  their  direction  of  growth,  by  both  gravity  and  light. 
The  branches  grow  in  the  dark  in  curves  which   take   the   most 


FlG.  20. — Fruit-body  of  Polyporus  squamosus  developed  on  a  log  in  entire 
absence  of  light,  three  weeks  old.  It  is  branched  and  sterile :  there  are 
no  signs  of  a  pileus.  Cf.  Figs.  1,  4,  and  5.  Reduced  to  f  natural  size. 

varied  directions  in  space,  and  show  no   definite  indications  that 
they  are  either  positively,  negatively,  or  transversely  geotropic. 

Light  from  a  small  hole  cut  in  the  dark-roorn  door  was  allowed 
to   fall   obliquely   on   to   the   log   upon   which   some    almost   fully 


ADJUSTMENTS   OF  FRUIT-BODIES  59 

developed  sterile  fruit-bodies  were  growing.  After  varying  the 
intensity  of  the  light  considerably  and  extending  the  experiment 
over  many  days,  I  was  unable  to  detect  any  change  in  the  direction 
of  growth  of  the  branches  in  response  to  the  illuminating  rays. 
In  being  unprovided  with  heliotropic  properties,  the  sterile  fruit- 
bodies  of  Polyporus  squamosus  present  a  marked  contrast  with 
those  of  Lentinus  lepideus. 

The  formation  of  the  pileus  is  brought  about  entirely  by  a 
morphogenic  stimulus  of  light.  To  this  kind  of  stimulus  the 
young  fruit-bodies  (although  not  the  older  sterile  ones)'  are  re- 
markably sensitive,  for,  when  some  of  them  were  temporarily 
exposed  to  daylight  for  only  a  single  hour  and  then  replaced 
in  the  dark-room,  they  subsequently  produced  pilei. 

In  the  development  of  a  pileus,  light  is  only  of  real  importance 
in  the  very  initial  stages.  Some  fruit-bodies  were  grown  on  a 
log  in  ordinary  daylight.  When  they  were  about  two  days  old  and 
the  pileus  on  each  was  yet  in  a  most  rudimentary  condition,  the 
log  was  placed  in  the  dark-room.  The  fruit-bodies,  thus  shut 
off  from  all  illumination,  continued  their  development,  attained 
a  considerable  size,  produced  hymenial  tubes,  and  liberated  millions 
of  spores.  Light  therefore  appears  to  give  a  sufficient  morphogenic 
stimulus  to  a  fruit-body  within  a  comparatively  lew  hours  after 
the  latter  has  come  into  existence.  It  unlocks  developmental 
forces  which,  when  once  set  free,  become  independent  of  the 
liberating  agent. 

In  the  light,  the  ends  of  the  conical  processes  after  flattening 
or  becoming  depressed,  quickly  expand  to  form  small  pilei  (Fig.  21, 
B  and  C ;  Plate  V.,  Figs.  32  and  33).  That  part  of  a  process  which 
bears  the  pileus  we  shall  now  refer  to  as  the  stipe. 

The  stipe  owes  its  position  in  the  first  instance  to  accident. 
However,  it  quickly  becomes  negatively  geo tropic  and  makes  an 
upward  curvature  so  as  to  bring  the  top  of  the  pileus  into  a 
horizontal  plane  (Fig.  21,  D).  When  this  has  taken  place  the 
pileus  becomes  diageotropic,  and  now  expands  rapidly  in  a  direction 
parallel  to  the  earth's  surface  (Fig.  21,  E;  Plate  V.,  Figs.  33  and  34). 
Subsequently  hymenial  tubes  develop  on  its  under  surface;  they 
are  positively  geotropic  and  grow  vertically  downwards.  These 


6o 


RESEARCHES   ON   FUNGI 


diverse  geotropic  phenomena  were  elucidated  by  placing  very  young 
or  half-grown  fruit-bodies  in  the  dark,  tilting  them  out  of  their 
normal  positions,  and  watching  their  development.  In  the  absence 
of  light,  stipes  curved  upwards,  hymenial  tubes  grew  downwards, 
and  the  pileus  flesh  extended  itself  horizontally  (Plate  V.,  Fig.  41). 


FlG.  21.  —  Polyporux  squam^sus.  The  embryology  of  fruit-bodies  with  eccentric 
pilei.  A-E,  vertical  sections  showing  successive  stages  in  development.  A, 
a  stromatous  knob  upon  which  a  conical  process  has  arisen.  B  and  C  show 
the  origin  of  the  pileus  by  depression  and  lateral  expansion  of  the  tip  of  a 
conical  process.  At  D  the  stipe  has  made  a  geotropic  curvature  so  that  the 
top  of  the  pileus  has  become  almost  horizontal.  The  pileus  has  now  begun 
its  eccentric  development.  E  is  a  fully-grown  fruit-body.  Its  pileus  is  very 
eccentric  and  has  developed  hymenial  tubes.  F-I,  young  fruit-bodies  seen 
from  above.  The  pilei  F  and  G  correspond  to  those  seen  at  B  and  C.  H,  a 
young  fruit-body  in  which  an  anterior  half  of  the  pileus,  a,  may  be  distin- 
guished from  a  posterior  half,  y.  The  stipe,  *.  is  laterally  placed  as  at  D.  I,  a 
young  fruit-body  in  which  the  anterior  half  of  the  pileus,  x,  is  growing 
rapidly,  whilst  the  posterior  half,  y,  has  ceased  development,  s,  the  stipe. 
All  £  natural  size. 


In  most  fruit-bodies  the  stipe  is  lateral  (Fig.  4,  p.  28),  in  a  few 
more  or  less  eccentric  (Plate  V.,  Fig.  426),  and  in  rare  instances 
quite  centrally  situated,  like  that  of  a  Mushroom  (Fig.  22).  An 
attempt  will  now  be  made  to  account  for  this  remarkable  variability 
of  form. 


ADJUSTMENTS   OF   FRUIT-BODIES  61 

The  shape  of  the  pileus  seems  to  be  partly  decided  by  the 
direction  of  the  conical  process  upon  which  it  develops.  When 
a  conical  process  happens  to  point  vertically  upwards  (as  it  very 
rarely  does),  the  stipe  to  which  it  gives  rise  is  vertical  and  the 


FlG.  22. — Polyporus  squumosus.     Under  surface  of  a  large  fruit-body  with  a  central 
stipe.     J  natural  size. 

pileus  horizontal  from  the  moment  of  their  differentiation  (cf. 
Plate  V.,  Fig.  35).  Under  these  circumstances,  since  the  internal 
developmental  forces  are  symmetrically  disposed,  the  pileus  simply 
grows  at  an  equal  rate  all  round  its  periphery.  In  response  to 
a  diageotropic  stimulus,  it  spreads  itself  out  in  a  horizontal  plane. 


62  RESEARCHES   ON  FUNGI 

When  the  fruit-body  becomes  full-grown,  it  thus  comes  to  have 
an  umbrella  shape  like  that  of  an  upright,  expanded  Mushroom 
(Fig.  22).  On  the  other  hand,  if  the  axis  of  the  conical  process 
upon  the  stromatous  knob  happens  to  be  inclined  upwards,  let 
us  suppose  at  an  angle  of  45°,  then  the  fruit-body  at  its  origin 
is  obliquely  set  (Fig.  21,  B;  Plate  V.,  Fig.  32).  The  young  stipe 
receives  a  directive  stimulus  from  gravity  and  grows  faster  below 
than  above.  It  therefore  gradually  bends  upwards  and  only  stops 
this  movement  when  the  top  of  the  pileus  has  been  turned  into 
a  horizontal  position  (cf.  Fig.  21,  D).  We  may  suppose  that  a 
morphogenic  stimulus  of  a  special  kind  is  conducted  to  the  pileus 
from  the  stipe  whilst  this  is  making  its  geotropic  curvature.  As 
a  reaction  to  this  stimulus  the  pileus  undergoes  a  physiological 
change  :  its  developmental  forces  become  reorganised.  It  can 
now  be  said  to  have  two  distinct  halves  differentiated  from  one 
another.  One  of  them  may  be  referred  to  as  anterior  in  position 
and  the  other  as  posterior.  The  former  is  always  the  half  which 
is  furthest  away  from  the  base  of  the  stipe  and  the  latter  the  one 
nearest  to  it  (Fig.  21,  F-I).  The  anterior  half  undergoes  rapid 
and  considerable  expansion,  but  the  posterior  half  soon  discontinues 
its  development.  In  the  mature  fruit-body,  in  this  instance,  the 
pileus  has  a  unilateral  position  like  that  shown  in  Fig.  4,  p.  28,  and 
in  Fig.  21,  E.  Slightly  eccentric  pilei  are  formed  when  their  stipes 
at  the  beginning  happen  to  be  nearly  vertical  but  not  quite.  The 
less  oblique  the  stipe,  the  less  will  be  the  physiological  differ- 
entiation induced  by  the  stipe  in  the  two  halves  of  the  pileus, 
and  the  more  nearly  in  the  end  will  the  fruit-body  approach  the 
umbrella  form.  If  the  foregoing  correctly  represents  what  takes 
place  during  development,  it  follows  that  the  form  of  a  fruit- 
body  is  indirectly  controlled  by  gravity.  The  radial  symmetry 
of  the  pileus  is  only  interfered  with  when  the  stipe  has  responded 
to  a  geotropic  stimulus.  The  degree  of  eccentricity  of  the  one 
part  seems  to  be  proportional  to  the  amount  of  curvature  undergone 
by  the  other  part. 

Since  the  unilateral  pilei  of  fruit-bodies  growing  on  the  trunks  of 
trees  are  directed  away  from  the  trunks  or  branches,  one  might  be 
inclined,  without  investigation,  to  think  that  this  is  due  in  part  to 


ADJUSTMENTS   OF  FRUIT-BODIES  63 

the  effect  of  light.  However,  it  was  found  that  when  very  young 
fruit-bodies  which  had  just  formed  pilei  in  the  light  were  placed  in 
various  directions  in  the  dark-room,  they  continued  their  develop- 
ment and  took  up  situations  relatively  to  their  substratum  similar  to- 
those  observed  in  nature  (Plate  V.,  Fig.  41).  Both  the  position 
assumed  by,  and  the  degree  of  symmetry  of,  a  fruit-body  are 
governed  by  gravity  alone.  However,  there  can  be  little  doubt 
that  light  exerts  a  tonic  influence  upon  the  pileus  during  its  develop- 
ment. When  a  half-grown  fruit-body  which  had  been  exposed  to- 
light  in  the  open  for  about  a  week  is  placed  in  the  dark  so  that  the 
plane  of  its  pileus  is  vertical,  the  flesh  grows  sharply  through  a  right 
angle  at  its  upper  margin,  and  thus  the  new  part  takes  up  a  position 
parallel  to  the  earth's  surface.  In  this  case  the  diageotropism  of  the 
pileus  is  very  marked.  If  a  very  young  fruit- body  which  has 
developed  in  the  light  for  only  two  or  three  days  (cf.  Plate  V., 
Figs.  32  and  33)  is  set  in  darkness,  the  pileus  often  grows  obliquely 
upwards  for  some  time  and  its  diageotropism  is  but  poorly  displayed 
(Plate  V.,  Fig.  42,  /).  If,  in  response  to  a  light  stimulus  of  about 
an  hour's  duration,  a  pileus  develops  upon  a  branch  of  a  stag's-horn- 
like  structure  which  is  still  growing  vigorously  and  is  looking 
upwards,  it  becomes  trumpet-shaped  in  the  dark  (Plate  IV.,  Figs.  40 
and  42,  d  and  e).  If  it  responds  to  the  stimulus  of  gravity  at  all,  it 
only  gives  an  obliquely  geotropic  reaction.  On  the  other  hand,  a 
symmetrical  pileus  grown  throughout  in  daylight  has  a  very  flat  top 
and  is  evidently  strongly  diageotropic  (cf.  Fig.  4,  p.  28,  and  Plate  V., 
Fig.  40).  It  thus  appears  that  the  geotropic  reaction  of  the  pileus 
flesh  is  partly  determined  by  the  amount  of  illumination  to  which 
a  fruit-body  is  exposed. 

When  a  stag's-horn-like  structure  has  grown  for  two  or  three 
weeks  in  the  dark,  and  has  almost  attained  its  full  extension,  it  can 
be  caused  to  form  patches  of  hymenial  tubes  on  its  under  surface  by 
exposure  to  sufficient  daylight  (Plate  V.,  Figs.  38  and  39).  The 
branched  fruit-body  thus  produced  presents  a  remarkable  contrast 
with  such  normal  ones  as  are  found  on  trees. 

A  feebly  developed,  trumpet-like  fruit- body  which  came  to- 
maturity  in  weak  light  (cf.  Plate  V.,  Fig.  40)  produced  hymenial  tubes 
both  on  the  lower  and  the  upper  surfaces  of  its  pileus  (Fig.  23).  A 


64  RESEARCHES   ON   FUNGI 

similar  disposition  of  hymenial  surfaces  has  been  observed  in  nature 
by  others  for  Hydnum  repandum.  Two  fruit-bodies  of  Polyporus 
varius  which  were  recently  brought  to  me,  had  a  quite  normal 
appearance  except  for  the  fact  that  very  shallow  hymenial  tubes  had 
developed  on  the  tops  of  the  pilei.  The  cause  of  the  formation  of 
these  monstrosities  still  remains  to  be  elucidated.  The  abnormal 
pileus  of  P.  squamosus  first  of  all  developed  hymenial  tubes  on 
its  under  surface.  As  it  continued  to  enlarge  it  gradually  fell  by 


FlG.  23. — Polyporus  squamosus.  Section  through  part  of  a  pileus 
with  hymenial  tubes  on  the  upper  as  well  as  on  the  lower 
surface.  About  £  natural  size. 

its  own  weight,  until  on  one  side  its  plane  looked  downwards  at  an 
angle  of  about  45°.  At  this  stage  a  new  layer  of  tubes  grew  upwards 
in  an  irregular  manner  on  the  pileus  top.  It  seems  likely  that  the 
unusual  displacement  of  the  fruit-body  in  some  way  initiated  this 
development. 

Owing  to  their  wonderful  power  of  undergoing  unilateral  de- 
velopment, the  fruit-bodies  of  Polyporus  squamosus  are  admirably 
adapted  for  securing  a  successful  liberation  of  their  spores.  The 
hymenial  tubes  come  to  look  downwards  upon  an  open  space  as  far 
from  the  tree  trunk  as  possible,  and  the  stipe  is  so  placed  that  it 


ADJUSTMENTS   OF  FRUIT-BODIES  65 

cannot  hinder  the   fall   of  the   spores,  or   their  dispersion  by  the 
wind. 

We  may  now  sura  up  the  adjustments  made  in  a  developing 
fruit-body  by  which  the  hymenial  surfaces  are  placed  in  the 
optimum  position  for  spore-discharge.  They  are  five  in  number : 

(1)  Slight  raising  of  the  pileus  by  growth  in  length  of  the  stipe; 

(2)  placing  the  top  of  the  pileus  in  a  horizontal  plane  by  a  curvature 
of  the  stipe ;  (3)  growth  of  the  pileus  parallel  to  the  earth's  surface  ; 
(4)  growth  of  the  pileus  with  a  symmetry  suited  to  the  position  of 
the  stipe ;   and  (5)  the  downward  growth  of  the  hymenial  tubes. 
The  first  of  these  adjustments  is  doubtless  due  to  internal  develop- 
mental causes  alone,  but  the  other  four  are  controlled  by  gravity. 

A  fruit-body  of  Polyporus  squamosus  owes  the  origin  of  its  pileus 
to  the  stimulus  of  light,  and  in  addition  it  responds  in  four  different 
ways  to  the  stimulus  of  gravity.  On  the  other  hand,  a  Mushroom  is 
indifferent  to  light  and  has  only  two  reactions  to  gravity.  The 
difference  between  the  two  species  in  the  number  of  responses  made 
to  external  stimuli  is  correlated  with  the  fact  that  the  one  fungus 
grows  on  a  tree  and  the  other  on  the  ground.  In  each  case  the 
dependence  on  external  forces  seems  to  be  of  the  simplest  kind 
to  meet  the  requirements  of  the  environment  in  a  successful 
manner. 

Coprinus  plicatilis. — The  small  fruit-bodies  of  this  species  were 
found  coming  up  on  a  lawn.  A  single  specimen  with  its  surrounding 
turf  was  taken  indoors,  and  immediately  placed  on  its  side  in  the 
position  shown  at  a  in  Fig.  24.  In  order  to  prevent  too  rapid 
transpiration,  the  turf  was  sprinkled  with  water  and  covered  with  an 
inverted  glass  dish.  In  two  hours  the  plane  of  the  pileus  had  been 
turned  by  the  stipe  through  an  angle  of  60°  (6),  and  in  three  hours 
it  had  become  almost  horizontal  (d).  To  my  surprise,  however,  the 
stipe  continued  its  curvature  for  an  hour,  until  the  pileus  had  become 
tilted  quite  20°  too  much  (/).  It  then  began  to  bend  back  again,  and 
in  the  course  of  a  further  hour  the  pileus  was  returned  for  the  second 
time  to  its  optimum  position  (k).  The  curvature  of  the  stipe,  how- 
ever, still  continued,  and  became  overdone  to  the  extent  of  about 
15°  0).  Again  the  stipe  rebent  itself,  and  for  the  third  time  the 
pileus  became  erect  (m).  After  this  the  stipe  overdid  its  curvature 


RESEARCHES   ON   FUNGI 


p  was 
f  the 


FIG.  24.—  Coprinui!  plicatilia.  Geotropic  swiu«-in»-  and  adjust- 
ment of  the  pilens  in  space.  A  fruit-body  was  placed 
in  the  position  shown  at  o,  and  after  2  hours  it  had 
assumed  the  position  shown  at  b.  The  sketches  b-o  were 
made  in  succession  at  intervals  of  half-an-hour. 
drawn  1  hour  after  o.  The  plane  of  the  base  o 
pilens  became  horizontal  after  3  hours  (d),  much  over- 
tilted  after4  hours(  f),  again  horizontal  after  5  hours(/<), 
much  over-tilted  asjaiu  after  6-6'5  hours  0'  and  fc).  asjain 
horizontal  after  7'5  hours,  very  slis-htly  over-tilted  for 
the  last  time  after  8  hours  (n),  and  finally  horizontal 
after  8'5  hours  (o).  The  horizontal  position  was  still 
maintained  after  9'5  hours  (p).  Natural  size. 


once  more  to  the  extent 
of  about  2°  (n).  It  then 
rebent  itself  for  the  fourth 
and  last  time,  and  brought 
the  plane  of  the  pileus 
into  a  horizontal  position, 
where  it  finally  remained 
(o  and  p).  The  sketches 
6  to  o  in  Fig.  24  were  all 
made  in  succession  at  in- 
tervals of  half-an-hour. 
The  formation  of  a  black 
spore-  deposit  beneath  the 
fruit  -  body  was  noticed 
subsequently  to  the 
stage  j. 

The  physiological 
swinging  of  a  fruit-body 
of  Coprinus  plicatilis 
about  its  objective  and 
final  position  forcibly 
reminds  one  of  the  oscil- 
latory movements  of  a 
pendulum  under  the 
action  of  gravity.  It 
finds  its  parallel  in  the 
well-known  geotropic  re- 
sponses of  shoots  in  the 
Phanerogamia.  We  are 
thus  provided  with  an- 
other striking  piece  of 
evidence  that  protoplasm 
has  the  same  fundamental 
characteristics  through- 
out the  vegetable  king- 
dom. A  further  investi- 
gation upon  the  pheno- 


ADJUSTMENTS   OF  FRUIT-BODIES  67 

menon  of  geotropic  swinging  will  be  recorded  in  connection  with 
an  account  of  Coprinus  plicatiloides. 

The  adjustments  of  a  fruit-body  of  Coprinus  plicatilw,  by  means 
of  which  the  successful  liberation  of  the  spores  is  secured,  are  three 
in  number :  (1)  The  erection  of  the  pileus  by  the  bending  of  the 
stipe ;  (2)  the  raising  of  the  pileus  by  elongation  of  the  stipe ;  and 
(3)  the  adjustment  of  the  gills  by  the  expansion  of  the  pileus.  The 
gills  do  not  appear  to  be  positively  geotropic.  Not  only  are  they 
small  in  size,  but  they  split  from  above  downwards  in  a  manner 
peculiar  to  many  species  of  Coprinus.  When  the  pileus  expands, 
they  open  out  like  the  folds  of  a  parasol.  It  is  clear  that  the 
hymenium  is  sufficiently  adjusted  to  a  suitable  position  by  the 
curvature  of  the  stipe  and  the  expansion  of  the  pileus.  A  reaction 
of  the  gills  to  gravity,  like  that  which  occurs  in  the  Mushroom, 
would  be  quite  unnecessary.  The  relations  of  the  fruit-bodies  with 
light  were  not  investigated. 

For  the  Coprini  generally,  there  appears  to  be  an  absence  of 
geotropic  response  in  the  gills.  This  peculiarity  is  correlated  with  a 
very  special  mode  of  spore-liberation  which  will  be  described  in 
detail  in  Chapter  XIX. 

Coprinus  niveus. — This  species  is  coprophilous,  and  is  frequently 
found  in  the  autumn  upon  horse  dung  in  fields.  The  fruit-bodies 
which  are  snowy  white,  make  their  appearance  at  any  place  on  the 
free  surface  of  the  dung  balls.  At  first  they  are  strongly  heliotropic 
and  with  unilateral  illumination  simply  grow  toward  the  source  of 
light.  This  heliotropic  response  enables  the  stipes  to  push  their 
unexpanded  and  conical  pilei  outwards  between,  or  from  under,  the 
dung  balls  into  the  open.  Growth  toward  the  source  of  light  con- 
tinues until  the  stipe  is  some  3-4  cm.  long.  Shortly  before  the 
pileus  begins  to  expand,  the  top  of  the  stipe  ceases  to  be  heliotropic 
and  becomes  negatively  geotropic:  it  makes  a  new  curvature  and 
grows  vertically  upwards.  This  adjustment  causes  the  whole  pileus 
with  its  gills  to  be  placed  in  the  requisite  position  for  the  successful 
liberation  of  spores.  Some  horse  dung  obtained  from  a  field  was  set 
so  that  the  fruit-bodies  found  growing  upon  it  looked  directly  up- 
wards. The  oblique  light  from  a  window  caused  the  stipes  to  make 
a  heliotropic  curvature  (Fig.  25,  to  the  left).  Afterwards,  when  the 


68  RESEARCHES   ON  FUNGI 

pilei  began  to  expand,  the  stipes  ceased  to  grow  toward  the  window, 
but  instead  grew  vertically  upwards.  On  the  right  side  of  Fig.  25  is 
shown  the  same  group  of  fruit-bodies  as  on  the  left  after  twelve 
hours'  further  development.  By  comparing  the  figures,  the  change 


FIG.  25. — Copnnua  nivcus.  Adjustments  of  the  pileus  in  space.  The  fruit-bodies 
grown  on  horse  dung  received  unilateral  illumination  from  a  window.  The 
young  stipes,  as  shown  on  the  left,  made  heliotropic  curvatures.  On  the  right 
the  fruit-bodies  are  twelve  hours  older  than  on  the  left.  As  soon  as  the  pilei 
began  to  expand,  the  stipes,  in  response  to  a  geotropic  stimulus,  grew  vertically 
upwards.  Stages  in  the  raising  of  the  pileus  by  elongation  of  the  stipe,  and  in 
the  expansion,  auto-digestion,  and  rolling  up  of  the  pileus  are  also  to  be  seen. 
Natural  size. 

which  took  place  in  the  direction  of  growth  of  the  stipes  may  be 
readily  realised. 

The  expansion  of  the  pileus  separates  the  gills  from  one  another, 
and  causes  the  hymenium  to  look  downwards  in  a  manner  similar  to 
that  described  for  Coprinus  plicatilis.  Here,  again,  the  gills  do 
not  require  to  adjust  themselves  in  vertical  planes  by  means  of  a 
geotropic  stimulus.  The  part  played  by  the  ':  deliquescence  "  of  the 
gills  and  the  folding  of  the  pileus  rim  over  the  top  of  the  pileus 


ADJUSTMENTS   OF  FRUIT-BODIES  69 

in  the  process  of  spore-liberation  will  be  sufficiently  discussed  in 
Chapter  XIX. 

The  adjustments  of  the  fruit-bodies  of  Coprinus  nivens  in  the 
interest  of  successful  spore-liberation  may  be  summed  up  as  follows : 
(1)  Heliotropic  curvature  of  the  stipe,  which  causes  the  pilei  to  be 
brought  out  of  crevices  in  the  substratum  into  the  open ;  (2)  erection 
of  the  pileus  by  a  negatively  geotropic  curvature  of  the  stipe; 
(3)  raising  of  the  pileus  by  elongation  of  the  stipe ;  (4)  adjustment 
of  the  gills  by  the  expansion  of  the  pileus ;  and  (5)  deliquescence 
of  the  gills  and  the  folding  of  the  pileus  rim  over  the  tqp  of  the 
pileus. 

Coprinus  plicatiloides,  Buller.1 — This  species,  like  the  foregoing 
one,  is  coprophilous  and  occurs  on  horse  dung.  Its  fruit-bodies  are 
often  very  tiny  and  rank  among  the  smallest  in  the  whole  group  of 
the  Agaricinese.  I  have  seen  specimens  less  than  1  cm.  long  and  with 
the  expanded  pileus  only  2  mm.  wide.  The  average  length  of  the 
stipe  is  about  3  cm.  and  the  width  of  the  pileus  about  5-6  mm.,  but 
in  large  individuals,  produced  on  sterilised  horse  dung,  these  dimen- 
sions may  be  doubled.  The  fruit-bodies  are  extremely  delicate  and 
can  only  stretch  their  stipes  and  expand  their  pilei  under  very  moist 
conditions.  When  exposed  to  moderately  dry  air  they  wither  up  in 
a  few  minutes.  The  life-history  of  the  fungus  requires  but  little 
time  for  its  completion.  Some  sterilised  horse-dung  balls  were 
infected  with  spores  and  kept  in  a  warm  room.  On  the  tenth  day 
after  infection  young  fruit-bodies  made  their  appearance,  and  by  the 
fourteenth  day  spores  were  being  freely  liberated. 

The  fruit-bodies  of  C.  plicatiloides  react  in  succession  to  the 
stimuli  of  light  and  gravity  in  the  same  manner  as  those  of 
C.  niveus.  One  evening,  a  fruit-body  which  had  begun  to  grow 
vertically  upwards  from  its  substratum  was  covered  over  with  a 
cap  of  stanniol  paper  opened  at  one  end  (Fig.  26,  A  and  B).  During 
the  night  the  upward  growth  continued.  Next  morning,  in  response 

1  This  name  has  been  given  for  the  sake  of  convenience  in  reference.  The 
fungus  was  obtained  at  Winnipeg.  I  have  not  been  able  to  identify  it  with  any 
described  species,  but  it  much  resembles  Coprinus  plicatilis.  Its  disc  is  depressed 
at  maturity,  as  in  C.  plicatilis,  but  it  is  narrow  instead  of  being  broad.  The  gills 
are  not  attached  to  a  collar,  and  the  spores  are  oval. 


RESEARCHES   ON  FUNGI 


to  unilateral  illumination,  the  stipe  made  a  positive  heliotropic 
curvature,  and  oblique  growth  toward  the  source  of  light  went  on 
all  day  (C  and  D).  When  darkness  supervened,  the  stipe  still  con- 
tinued to  grow  in  the  direction  it  had  taken  up  during  the  previous 
day.  Toward  morning  on  the  next  day,  it  gradually  curved  verti- 
cally upwards,  thereby  indicating  that  it  had  become  geotropically 
sensitive.  After  the  stipe  had  been  growing  away  from  the  earth's 
centre  for  about  three  hours,  the  pileus  expanded  in  a  horizontal 
plane  and  discharged  its  spores  (E).  Spore- discharge  lasted  for 
about  an  hour  and  a  half.  Soon  after  its  completion  the  fruit-body 


FIG.  26. —  Coprinus  pHcatiloid.es.  Avoidance  of  an  obstacle  by  successive  reactions 
to  the  directive  stimuli  of  light  and  gravity.  A,  paper  cap  shown  in  B-E  in 
section.  B,  young  fruit-body  covered  with'the  paper  cap  on  the  afternoon  of 
the  first  day.  C,  the  fruit-body  at  daybreak  on  the  second  day  :  the  arrow 
shows  the  direction  of  the  chief  incident  rays  of  light  D,  the  fruit-body 
at  the  end  of  the  second  day.  E,  the  fruit-body  about  noon  on  the  third 
day.  Natural  size. 

collapsed.  The  successful  avoidance  of  an  obstacle  and  subsequent 
uplifting  of  the  pileus,  as  illustrated  by  the  experiment  just  recorded, 
affords  excellent  evidence  of  the  biological  importance  of  the  re- 
actions of  the  fruit-body  to  external  stimuli. 

In  order  to  test  the  sensitiveness  of  the  stipe  to  the  stimulus  of 
gravity,  a  vertical  fruit-body,  attached  to  its  dung  ball,  was  tilted 
into  a  horizontal  position.  A  distinct  reaction  was  noticed  in  about 
1 0  minutes,  and  the  pileus  was  raised  into  the  erect  position  again  in 
1  hour  15  minutes.  By  using  specimens  a  little  less  developed,  a 
greater  sensitiveness  was  observed  :  the  plane  of  the  base  of  the 
pileus  was  turned  from  the  vertical  to  the  normal  horizontal  position 


ADJUSTMENTS   OF  FRUIT-BODIES  71 

in  45  minutes.  After  further  practice  in  handling  the  material  and 
in  making  observations,  I  found  a  fruit-body  which  curved  upwards 
through  a  right  angle  in  17*5  minutes.  It  gave  a  distinct  macro- 
scopic reaction  to  the  stimulus  of  gravity  after  3  minutes'  stimulation, 
turned  through  an  angle  of  10°  in  the  first  5  minutes,  and  through  a 
further  angle  of  80°  in  the  next  12-5  minutes.  The  pileus,  therefore, 
was  turned  through  almost  a  complete  right  angle  with  an  angular 
velocity  greater  than  that  of  the  minute  hand  of  a  clock.  This 
angular  velocity  is  far  greater  than  that  known  for  any  Phanerogam 
or,  indeed,  any  other  plant  when  stimulated  by  gravity.  For  a  stem 
to  turn  upwards  through  a  right  angle  several  hours  are  usually 
required,  whereas,  as  we  have  seen,  the  stipe  of  Coprinus  plicatiloides 
can  perform  this  movement  in  17'5  minutes.  The  latent  period  for 
roots — the  time  required  for  the  commencement  of  curvature  after 
continuous  geotropic  stimulation — is,  according  to  Moisescu,1  who 
experimented  on  Lupinus  albus,  Cucurbita,  &c.,  at  least  15  minutes 
when  one  observes  with  the  naked  eye.  On  the  other  hand,  the 
stipe  of  the  Coprinus  made  a  distinct  curvature  in  3  minutes.  The 
remarkable  rapidity  of  the  geotropic  reaction  in  the  fungus  is  com- 
parable with  the  reactions  of  tendrils  to  the  stimulus  of  touch.2 

Moisescu 3  states  that  with  the  microscope  he  could  detect  a 
slight  downward  curvature  of  certain  roots  after  one  minute  of 
stimulation.  In  an  experiment  in  which  a  fruit-body  was  tilted  to  an 
angle  of  45°  and  the  stipe  supported  on  a  rest  so  as  to  prevent  its 
initial  sagging  from  the  weight  of  the  pileus,  a  distinct  upward 
curvature  was  observed  with  a  horizontal  microscope  of  low  magnifi- 
cation in  one  and  a  half  minutes.  Probably  further  experiments 

1  Moisescu,  "  Kleine  Mitteilung  iiber  die  Anwendung  des  horizontalen  Micro- 
skopes  zur  Bestimmung  der  Reaktionszeit,"  Ber.  d.  deutschen  bot.  Gesell.,  Bd.  XXIII., 
1905,  p.  366. 

2  The  movements  of  very  sensitive  tendrils  in  certain  species  are  even  more 
rapid  than  that  observed  for  the  stipe.     Thus,  after  rubbing  the  inner  side  of  a 
tendril  of  a  Cucumber  and  placing  the  rubbed  surface  in  contact  with  a  stick,  I 
observed  that  the  tendril  made  a  half-turn  round  its  support  in  five  minutes,  a 
whole  turn  in  ten  minutes,  and  one  and  a  half  turns  in  twenty  minutes.     The 
temperature  was  85°  F.     The  mean  angular  velocity  of  the  tendril  for  the  first 
ten  minutes  was  36  times  greater  than  that  of  the  stipe,  although  after  twenty 
minutes  it  had  become  only  5'5  times  greater. 

3  Moisescu,  loc.  cit. 


72  RESEARCHES   ON   FUNGI 

would  show  that  the  latent  period  for  the  fungus  stipes  is  quite  as 
short,  if  not  shorter,  than  that  for  roots. 

Already,  in  describing  the  adjustments  of  Coprinus  plicatilis, 
we  have  become  acquainted  with  the  fact  that  a  stipe  which  has 
been  displaced  from  a  vertical  position  performs  a  series  of  geo- 
tropic  oscillations  before  again  coming  to  rest.  A  similar  pheno- 
menon occurs  with  Coprinus  plicatiloides,  but  in  this  species  the 
oscillations  sometimes  take  place  in  surprisingly  short  intervals  of 
time.  In  one  experiment  a  fruit-body  was 
moved  from  a  vertical  to  a  horizontal  posi- 
tion whilst  the  stipe  was  rapidly  growing  in 
length  (Fig.  27,  a).  The  plane  of  the  base 
of  the  pileus  became  turned  upwards  through 
a  right  angle  in  1  hour  and  15  minutes  (6). 
However,  the  curvature  of  the  stipe  was  con- 
tinued for  half-an-hour  until  the  pileus  plane 
had  become  tilted  up  to  a  maximum  angle 
of  41°  (c).  The  stipe  then  began  to  make  a 
FIG.  27.— Geotropic  reaction  reverse  curvature,  and  in  the  course  of  an 

of  the  stipe  of  Coprinus    .  ,        .     ..  .          ,       ..  •       -,    • 

The  fruit-   hour  and  a  halt  'gradually  regained  its  ver- 
tical    P°sition-      Its    oscillatory    movements 
position,  a.    b-d,  subse-  then  ceased.     The  pileus,  which  at  this  stage 

quent    positions    of    the 

fruit-body :  b,  after  i  hr.  had  already  become  partially  expanded,  then 

15   mins. ;   c,  after  1   hr.  j  .,      i  r         ,    .  u  .LIT 

45  mins. ;  d,  after  about  spread  itself  out  in  a  horizontal  plane  and 

oAhe  plaSTof  the  base    liberated  its   sPores   (d)'      Ifc  seems  somewhat 

of  the  pileus,  shown  at  c,  remarkable  that,  in  the  attempt  to  bring  the 

was  41°.     Natural  size. 

pileus  into  its  optimum  position  for  liberat- 
ing the  spores,  although  the  first  geotropic  reaction  was  so  remark- 
ably overdone,  the  second  should  have  resulted  in  such  complete 
success.  The  second  adjustment  was  accompanied  by,  and  probably 
affected  by.  the  opening  of  the  pileus. 

The  most  interesting  case  of  geotropic  oscillations  was  observed 
with  the  already  mentioned  very  sensitive  fruit-body  which  turned 
upwards  through  a  right  angle  in  17'5  minutes  after  displacement. 
The  stipe  executed  no  less  than  five  oscillations  about  its  normal 
position  (Fig.  28).  The  successive  geotropic  supracurvatures  were 
28°,  8°,  3°,  1°,  and  0°.  The  swing  past  the  normal  position  in  each 


ADJUSTMENTS   OF   FRUIT-BODIES 


73 


oscillation  was  therefore  about  one-third  of  the  previous  swing  up 
to  the  normal  position.  Each  succeeding  oscillation  was  made  in 
less  time  than  its  predecessor,  and  the  whole  series  of  movements 
was  completed  in  an  hour  and  a  quarter.  In  making  observations 
upon  the  amount  of  curvature,  advantage  was  taken  of  the  fact 
that  the  plane  of  the  base  of  the  pileus,  viewed  horizontally,  appears 
as  a  straight  line  (cf.  Fig.  27).  The  tilt  of  this  line  was  measured 
by  placing  a  sliding  lever  parallel  to  it,  and  then  reading  off  the 


\ 

\ 

6(1° 

' 

\ 

{•ft 

\ 

(  (f 

\ 

7(T 

\ 

1 

\ 

1(1° 

1 

\ 

Q 

* 

\ 

s 

^ 

^ 

I 

M< 

8 

•a. 

I 

16 

\ 

Q 

36 

JX 

Jt 

^ 

u 

V 

« 

•**— 

no° 

\ 

/ 

10' 

V-*. 

^x 

t.o 

FIG.  28. — Eesults  of  observations  on  the  movements  of  a  fruit-body  of  Coprinus  plicati- 
loidcs  about  its  normal  position  in  response  to  the  stimulus  of  gravity.  The  fruit- 
body  at  the  beginning  of  the  experiment  was  turned  from  a  vertical  in  to  a  horizontal 
position.  The  ordinate  gives  the  inclination  of  the  axis  of  the  end  of  the  stipe  to 
the  vertical  in  degrees  and  the  abscissa  the  time  in  minutes.  The  curve  drawn 
through  the  observation  points  shows  that  the  fruit-body  executed  a  series  of 
damped  oscillations. 

deflection  from  a  horizontal  plane  by  means  of  a  surveyor's  pro- 
tractor. Since  the  axis  of  the  end  of  the  stipe  is  always  perpen- 
dicular to  the  plane  of  the  base  of  the  pileus,  the  divergence  of 
the  latter  from  the  horizontal  gives  the  divergence  of  the  former 
from  the  perpendicular.  The  fruit-bodies,  attached  to  their  horse- 
dung  balls,  were  kept  in  a  covered  glass  vessel  in  order  to  prevent 
loss  of  moisture.  The  laboratory  temperature  was  20°  C.  The 
deflections  of  the  stipe  from  the  vertical  at  successive  periods  of 


74  RESEARCHES   ON   FUNGI 

time  are  plotted  out  in  Fig.  28.  The  resulting  curve  is  one  of 
damped  oscillations,  roughly  resembling  that  of  a  pendulum  swing- 
ing in  a  viscous  medium.  Some  of  the  results  plotted  do  not  lie 
on  the  curve.  I  have  reason  to  suppose  that  this  is  due  not  to 
irregularities  of  growth,  but  to  errors  in  making  the  observations. 
Greater  accuracy,  doubtless,  would  have  been  obtained  if  an  assistant 
had  recorded  times  whilst  I  recorded  angles,  but,  unfortunately,  in 
the  absence  of  help,  it  was  necessary  for  me  to  make  the  two  sets 
of  measurements  by  myself.  Both  alertness  and  correctness  of 
judgment  are  required  in  order  to  place  a  sliding  lever  parallel  to 
the  pileus  plane.  Practice,  however,  enables  one  to  make  the 
necessary  readings  with  considerable  precision. 

In  the  development  of  the  fruit-bodies  in  my  laboratory  an 
undoubted  periodicity  was  observed.  A  few  fruit-bodies  expanded 
each  morning  and  shed  their  spores  during  the  mid-day  hours, 
usually  between  12  and  3  o'clock.  In  properly  cared  for  cultures  I 
could  never  find  fruit-bodies  opened  at  night.  Successive  crops 
of  mature  fruit-bodies  were  thus  produced  with  a  diurnal  rhythm. 
A  similar  rhythm  is  well-known  for  Pilobolus ;  and  in  Ascobolus 
a  few  asci  ripen  and  burst  each  day.  The  stretching  of  the  spor- 
angiophore  of  Pilobolus,  and  of  a  group  of  asci  in  Ascobolus,  is 
put  off  until  morning,  so  that  light  may  be  used  to  direct  the 
growth  of  these  heliotropic  structures  toward  an  open  space.  If 
the  orientation  of  the  fungus  guns  were  to  take  place  at  night,  its 
successful  accomplishment  would  be  simply  a  matter  of  chance. 
In  Coprinus  plicatiloidcs  the  stipe  is  too  massive  a  structure  to 
be  fully  developed  in  one  morning.  Its  partial  elongation  and 
curvature  toward  an  open  space  in  response  to  the  stimulus  of 
light,  take  place  on  the  day  previous  to  spore-discharge.  On  the 
next  morning  it  erects  the  pileus  in  response  to  the  stimulus  of 
gravity.  It  is  clearly  of  advantage  that  the  stipe  shall  begin  to 
elongate  in  the  daytime  rather  than  at  night,  for  the  first  requisite 
for  the  successful  functioning  of  a  fruit-body  is  that  the  pileus 
shall  be  brought  into  the  open.  The  rhythmic  development  of 
the  fruit-bodies  of  all  the  three  coprophilous  fungi  seems,  there- 
fore, to  be  of  distinct  importance  in  facilitating  the  scattering  of 
the  spores. 


ADJUSTMENTS   OF  FRUIT-BODIES  75 

A  diurnal  rhythm  in  the  development  of  the  fruit-bodies  of 
small  and  ephemeral  Coprini  occurs  not  merely  in  the  laboratory 
but  also  in  nature.  I  have  noticed  it  more  particularly  in  the  case 
of  Coprinus  plicatilis  growing  on  a  lawn.  A  few  fruit-bodies  came 
to  maturity  toward  each  noon  for  a  succession  of  20-30  days. 
Worthington  Smith1  noticed  the  same  phenomenon  for  Coprinus 
radiatus  growing  on  a  manure  heap.  He  states  that  "at  seven 
or  eight  in  the  evening  nothing  but  immature  plants  can  be  seen ; 
about  eleven  or  twelve  a  rapid  growth  commences,  and  by  two 
or  three  o'clock  in  the  morning  perfect  maturity  is  reached.  If 
the  morning  is  moist  the  plants  will  remain  in  perfection  till  nine 
or  ten  o'clock,  but  if  it  is  dry  they  will  not  last  after  five  or  six." 
According  to  these  observations,  in  nature  the  fruit-bodies  of 
Coprinus  radiatus  may  shed  their  spores  before  daylight  appears. 
If  this  is  so,  strong  support  is  given  to  my  view  that  the  importance 
of  the  periodic  development  lies,  not  in  spore-liberation  occurring 
at  any  particular  time,  but  in  the  fact  that  the  beginning  of  the 
stretching  of  the  stipe  is  arranged  to  take  place  whilst  light  can 
be  used  as  a  directive  stimulus. 

The  adjustments  of  the  fruit-bodies  of  Coprinus  plicatiloides 
in  the  interests  of  spore-liberation  may  be  summed  up  as  follows: 

(1)  Heliotropic  curvature  of  the  stipe,  which  causes  the  pilei  to 
be    brought   out   of  crevices    in    the   substratum    into    the    open ; 

(2)  erection  of  the  pileus  by  a  negatively  geotropic  curvature  of 
the  stipe;    (3)  raising  of  the  pileus  by  the  elongation  of  the  stipe; 
and  (4)  adjustment  of  the  gills  by  the  expansion  of  the  pileus. 
There  is  no  deliquescence  of  the  gills,  and  on  this  account   the 
fruit-bodies  of  Coprinus  plicatiloides    have   one    adjustment   less 
than  those  of  Coprinus  niveus. 

General  Remarks.— A  number  of  otherwise  very  different  copro- 
philous  fungi  resemble  one  another  in  reacting  to  light.  Thus  we 
find  that  positive  heliotropic  curvatures  are  made,  not  only  by  the 
stipes  of  the  Coprini,  but  also  by  the  sporangiophores  of  Mucor, 
Phycomyces,  and  Pilobolus,  by  the  asci  of  Ascoboli,  and  by  the 
perithecial  necks  of  Sordarite.  These  responses  to  light  are  adrnir- 

1  W.  Smith,  "Reproduction  in  Coprinus  radiatus"  Grevillea,  vol.  iv.,  1875-76, 
p.  54. 


RESEARCHES   ON   FUNGI 


ably  adapted  to  permit  of  organs  of  reproduction,  which  are  pro- 
duced on  an  irregularly  disposed  substratum,  liberating  their  spores, 
so  that  they  may  freely  escape  from  their  place  of  origin. 

Probably  all  the  coprophilous  Coprini  are  heliotropic,  since  they 
all  grow  on  the  same  peculiarly  irregular  substratum.  However 
Coprinus  comatus,  which  comes  up  on  turf  in  fields,  &c.,  appears 
to  be  without  response  to  light.  When  the  fruit-bodies  receive 
unilateral  illumination,  the  stipes  do  not  make  a  heliotropic  cur- 

^^^^^___     ,        --I^^^^^^M^M^^M    vature  (cf.  Figs.  69 

and  70,  pp.  198, 199). 
As  with  the  Mush- 
room, heliotropism 
would  be  without 
advantage.  The 
fields  in  which  the 
fruit-bodies  come  up 
are  on  the  average 
horizontally  dis- 
posed. In  order  to 
raise  the  pilei,  so 
that  they  become 
free  from  surround- 
ing obstacles,  re- 
sponse to  the  stimu- 
lus of  gravity  is  all 
that  is  necessary. 

Anellaria  separ- 
ata (Fig.  32,  p.  80) 
is  also  coprophilous  in  habit,  and  in  general  form  its  fruit-bodies 
resemble  those  of  coprophilous  Coprini.  In  the  field  the  stipes  are 
usually  vertical.  When  a  mature  fruit-body  liberating  spores  is 
tilted,  the  top  of  the  stipe  is  still  capable  of  responding  to  a  geotropic 
stimulus.  The  peculiar  appearance  of  a  full-grown  fruit-body  which 
has  been  tilted  and  has  readjusted  itself  is  illustrated  in  Fig.  29. 

On  tilting  the  very  small  fruit-bodies  of  Omphalia  fibula  which 
are  to  be  found  on  lawns,  &c.,  I  have  been  unable  to  detect  any 
geotropic  response  in  the  narrow  decurrent  gills.  In  this  species, 


FlG.  29. — Anellaria  separata.  Geotropic  reaction  of  the 
stipe.  To  the  left  is  a  fruit-body  of  a  closely  allied 
species,  Pansenlus  phalaenarum.  To  the  right  are  two 
fruit-bodies  of  Anellaria  separata  which  resembled  in 
form  that  on  the  left.  After  they  had  been  set  in 
oblique  positions  the  pilei  became  readjusted  by  curva- 
tures made  by  the  tops  of  the  stipes.  ^  natural  size. 


ADJUSTMENTS   OF  FRUIT-BODIES  77 

and  probably  also  in  certain  others  where  the  fruit-bodies  are 
diminutive,  there  is  only  one  response  to  gravity,  namely,  that 
of  the  stipe.  This  is  sufficient  to  place  the  tiny  pilei  so  accurately 
in  the  erect  position  that  the  gills  look  downwards  and  successful 
spore-liberation  can  take  place.  In  larger  ground  Agaricinese  with 
deep  gills,  e.g.  the  Mushroom,  an  extra  response  is  requisite, 
namely,  that  of  the  gills  themselves.  The  most  complex  of  all 
Agaricineae  in  relation  to  gravity,  doubtless,  are  certain  large 
species,  such  as  Pleurotus  ostreatus  (Figs.  2  and  3,  pp.  22  and  23), 
which  grow  on  trees  and  stumps.  These  probably  have  four  geo- 
tropic  reactions  similar  to  those  already  discussed  for  Polyporus 
squafmosus ;  (1)  Negative  geotropism  of  the  stipe;  (2)  diageotropism 
of  the  pileus  flesh;  (3)  eccentricity  of  development;  and  (4) 
positive  geotropism  of  the  gills. 

It  is  the  rule  with  Hymenoinycetes  that  the  mycelium  gives 
rise  to  a  great  many  more  rudimentary  fruit-bodies  than  can 
possibly  come  to  maturity.  On  a  Mushroom  bed  one  may  often 
observe  some  hundreds  of  such  rudiments  within  the  space  of  a 
few  square  inches;  and  even  in  Polyporus  squamosus  the  rudi- 
ments are  generally  at  least  twice  as  numerous  as  the  mature 
fruit-bodies  (Plate  V.,  Fig.  31-34).  It  generally  happens  that  a 
very  limited  number  of  the  rudimentary  fruit-bodies  obtain  the 
advantage  over  their  fellows  and  commence  to  grow  rapidly.  The 
food  supply  is  thus  drawn  to  them,  and  the  unsuccessful  rudi- 
ments at  once  cease  their  development  and  become  aborted.  The 
production  of  a  great  many  rudiments  at  the  beginning  of  repro- 
duction increases  the  chance  that  some  of  them  will  be  suitably 
situated  for  successful  development.  In  some  species,  it  generally 
happens  that  a  number  of  rudiments  continue  their  development 
side  by  side,  so  that  at  maturity  the  fruit-bodies  are  more  or  less 
crowded.  The  crowding  in  Collybia  velutipes,  Coprinus  micaceus, 
and  Armittaria  mellea  (Fig.  30),  &c.,  may  become  so  excessive 
that  a  large  proportion  of  the  spores  produced  are  prevented  from 
escaping  from  the  fruit-bodies.  Such  overcrowding  seems  to  be 
a  distinct  imperfection  in  fungus  development. 

We  may  summarise  the  general  conclusion  from  the  observa- 
tions recorded  in  this  chapter  as  follows.  The  fruit-bodies  of  the 


78  RESEARCHES   ON  FUNGI 

Hymenomycetes  during  development  execute  a  set  of  complex 
growth  movements  which  are  partly  controlled  by  internal  causes 
and  partly  by  external  stimuli.  These  movements  are  correlated 
with  the  general  structure  of  the  fruit-bodies,  and  with  the 


FIG.  30. — ArmiUaria  mellea.  Overcrowded  group  of  fruit- 
bodies  growing  on  a  living  Mountain  Ash  (Pints 
Aucuparia}.  Photographed  at  Sutton  Park,  Warwick- 
shire, by  J.  E.  Titley.  About  J  natural  size. 

position  of  the  surface  of  the  substratum  on  which  each  species 
grows.  The  result  of  the  movements  in  all  cases  is  to  place  the 
hymenium  in  such  a  position  that  it  can  discharge  its  spores,  so 
that  they  may  fall  freely  downwards  into  an  open  space  from 
which  they  may  be  carried  off  by  the  wind. 


CHAPTER    V 

SPORE-DEPOSITS— THE   NUMBER  OF  SPORES 

ALTHOUGH  the  spores  of  Hymenomycetes  under  ordinary  circum- 
stances are  too  small  to  be  seen  individually  with  the  naked  eye, 
yet,  when  collected  together  in  large  numbers,  they  cari  readily 
be  recognised  in  the  form  of  a  powder.  In  order  to  obtain  a 
spore-deposit  of  this  nature,  one  simply  takes  a  pileus,  from  which 


FiG.  31. — Spore-deposit  produced  in  about  twenty  hours  from  a  pileus  of 
Lepiota  rachodes.  (The  central  parts  of  some  of  the  gills  were  in  contact 
with  the  paper:  hence  slight  disturbances  to  the  regularity  of  the 
deposit.)  Natural  size. 

the  stipe  has  been  removed,  and  places  it  upon  a  sheet  of  paper. 
On  this  the  falling  spores  rapidly  accumulate.  Owing  to  their 
pronounced  adhesiveness,  they  cling  to  one  another  and  to  any  sur- 
face with  which  they  come  into  contact  with  considerable  tenacity. 
Spore-deposits  cannot  therefore  be  shaken  off  paper  or  glass  upon 
which  they  have  been  collected. 


RESEARCHES   ON   FUNGI 

In  still  air,  spores,  after  leaving  the  hymenial 
surfaces,  fall  vertically  downwards  at  the  rate  of 
about  1-5  mm.  per  second.1  If,  therefore,  one 
takes  the  precaution  to  eliminate  small  convec- 
tion currents  by  covering  the  pilei  placed  on 
paper  with  small  glass  vessels,  one  can  produce 
a  spore  print  of  the  gills  or  hymenial  tubes,  &c. 
Such  spore  prints  are  shown  in  Figs.  31  and 
33.  In  the  first  one  the  white  spores  of  Lepiota 
rackodes  were  collected  on  black  paper,  whilst  in 
the  second  the  black  spores  of  Anellaria  separ- 
ata were  collected  on  white  paper.  The  radiating 
spore  lines  correspond  to  spaces  between  the  gills. 

The  rate  of  accumulation  of  a  spore-deposit 
depends  on  various  factors,  such  as  the  fungus 
species,  age  of  the  pileus,  temperature,  &c.  How- 
ever, one  may  often  obtain  a  recognisable  spore 
print  in  the  short  space  of  fifteen  minutes 
(Fig.  33,  A).  As  the  spores  fall  continuously, 
usually  for  days  together,  the  deposits  become 
denser  and  denser  as  time  goes  on  (Fig.  33,  B 
and  C).  By  moving  a  pileus  from  one  place  to 
another  every  hour  and  thus  procuring  successive 
spore  prints,  one  may  readily  convince  oneself  of 
the  continuity  and  regularity  of  spore-emission. 

When  a  pileus  is  raised  above  the  paper  and 
spore-deposition  takes  place  under  a  beaker  or 
relatively  large  glass  vessel,  the  spore-deposit  no 
longer  gives  a  print  of  the  gills  but  has  a  cloudy 
appearance  (Fig.  34,  A).  The  reason  for  this  is 
that  the  air,  through  which  the  spores  fall,  is  not 
perfectly  still  but  is  undergoing  slow  convection 
movements.  The  spores,  therefore,  are  unable 
to  fall  quite  vertically.  In  Fig.  34,  A,  is  shown 
FIG.  32.  -Amiiaria  sepa-  a  deposit  from  a  pileus  of  Anellaria  separata 

rata.    After  removal  of        .      \ 

the  stipes,  pilei  of  fruit-  raised  2  cm.   above  the   paper.      Ihe   accumu- 

bodies    of    this    species 

the  spore-deposits  shown  x  Vide  infra,  Chaps.  XV.  and  XVI. 

inFi<rs.33aud34.  About 
natural  size. 


SPORE-DEPOSITS 


81 


lation  of  the  spores  took  place  under  a  large  tumbler  during  a 
night.  In  Fig.  34,  B,  one  sees  that  the  gills  are  not  perfectly 
outlined.  In  this  case  the  rim  of  the  pileus  did  not  quite 
touch  the  paper  all  round.  The  pileus  was  exposed  on  a  table, 


FiU.  33. — Spore-deposits  from  a  pileus  of  Andlaria  separata.  A  pro- 
duced in  fifteen  minutes,  B  in  one  hour,  and  C  in  six  hours. 
Photographed  natural  size. 

and  therefore  affected  by  convection  currents  slowly  sweeping 
beneath  it.  The  result  of  this  was  a  slight  displacement  of  the 
falling  spores.  In  Fig.  34,  C,  there  is  shown  a  deposit  made  under 
a  tumbler  in  the  course  of  four  hours  from  a  perfect  pileus,  the 


FlG.  34.— Spore-deposits  from  three  pilei  of  Andlaria  separata  showing  the 
effect  of  convection  currents.  Explanation  in  the  text.  Photographed 
natural  size. 

rim  of  which  was  in  contact  with  the  paper  throughout.  Here 
the  spores  fell  vertically  downwards,  and  have  therefore  given  an 
excellent  print  of  the  gills.  If  one  allows  spores  to  fall  from 
small  pieces  of  pilei  placed  in  specially  constructed  chambers, 


82  RESEARCHES   ON  FUNGI 

designed  to  reduce  convection  currents  to  the  least  possible 
minimum  (Fig.  58,  p.  167,  and  Fig.  62,  p.  182),  spore  prints  of  the 
gills  can  be  obtained  when  the  gills  are  2-10  cm.  above  the 
collecting  surfaces. 

It  seemed  of  interest  to  determine  the  number  of  spores  liberated 
from  a  few  typical  fruit-bodies.  It  has  often  been  stated  that 
Mushrooms,  &c.,  produce  spores  by  the  million.  That  this  is  no 
exaggeration  will  be  clear  from  an  account  of  an  investigation  into 
the  number  of  spores  produced  by  fruit-bodies  of  Psalliota  cam- 
pestris,  Coprinus  comatus,  Polyporus  squamosus,  and  Deedalia 
confragosa. 

Psalliota  campestris. — Fruit-bodies  just  about  to  liberate  their 
spores  were  obtained  from  a  field.  The  stipe  of  one  specimen  was 
cut  off,  and  its  pileus,  which  had  a  diameter  of  8  cm.,  was  placed 
in  contact  with  a  sheet  of  white  paper.  A  suitable  covering  was 
used  to  keep  off  air-currents.  In  two  days  the  discharge  of  spores 
appeared  to  be  completed. 

The  paper  containing  the  spores  was  placed  in  100  cc.  of  distilled 
water,  and  the  whole  stirred  vigorously  until  the  spores  had  been 
washed  off  the  paper  and  spread  evenly  through  the  fluid.  A 
Leitz-Wetzlar  counting  apparatus  was  then  employed  and  the 
number  of  spores  which  settled  on  the  squares  carefully  counted. 
As  a  result  of  a  number  of  trials,  it  was  calculated  that  the  spore- 
deposit  represented  approximately  1,800,000,000  spores.  Since  all 
these  spores  fell  within  forty-eight  hours,  we  must  conclude  that 
on  the  average  about  40,000,000  fell  during  each  hour  of  the 
spore-fall  period. 

Coprinus  comatus. — In  calculating  the  number  of  spores  in  this 
species,  a  more  direct  method  was  employed  than  that  described 
above.  A  gill  of  Coprimes  comatus  can  easily  be  split  down  its 
median  plane.  If,  by  taking  advantage  of  this  fact,  one  obtains 
half  a  gill  and  then  places  it  in  a  closed  compressor  cell  so  that 
the  hymenium  looks  upwards,  one  can  easily  observe  the  basidia 
and  spores  with  the  microscope.  They  form  a  very  regular  and 
striking  pattern  (Plate  III.,  Fig.  15).  With  the  aid  of  a  drawing 
apparatus,  it  was  found  that  the  number  of  basidia  on  O'Ol  of  a 
square  millimetre  was  34,  where  the  spores  were  ripening.  As 


THE   NUMBER   OF  SPORES  83 

each  basidium  bears  four  spores,  it  was  calculated  that  the  number 
of  spores  on  1  sq.  mm.  was  13,600. 

The  fruit-body  used  for  this  investigation  was  a  large  one  (cf. 
Plate  I.,  Fig.  1).  The  pileus  was  12  cm.  high  and  possessed  214 
gills.  Each  gill  had  an  area  of  hymenial  surface  on  its  two  sides 
of  1800  mm.  A  simple  calculation,  therefore,  showed  that  each 
gill  had  produced  about  24,480,000  spores,  and  that  the  number  of 
spores  for  the  whole  fruit-body  amounted  to  the  enormous  approxi- 
mate total  of  5,240,000,000.1  The  period  of  spore-discharge  for 
large  fruit-bodies  of  Coprinus  comatus  was  found,  by  making  field 
observations,  to  last  about  forty-eight  hours.  On  the  average, 
therefore,  the  fruit-body  investigated  would  have  shed  100,000,000 
spores  each  hour  of  spore-fall. 

In  the  Coprini  it  is  very  easy  to  count  the  basidia  on  the 
gills,  for  adjacent  basidia  on  any  small  part  of  a  gill  are  practi- 
cally in  exactly  the  same  state  of  development,  and  are  set  at 
regular  intervals  among  the  paraphyses.  For  other  Agaricinese, 
e.g.  Psalliota  campestris,  this  method  does  not  succeed  owing  to 
the  fact  that  adjacent  basidia  at  any  one  time  are  in  the  most 
diverse  stages  of  development. 

Polyporus  squamosus. — A  fresh  fruit-body,  which  had  just 
reached  maturity,  was  removed  from  a  tree  and  placed  with  its 
spores  downwards  upon  a  piece  of  smooth  brown  paper.  Upon 
this,  after  falling  down  the  hymenial  tubes,  the  spores  gradually 
accumulated  in  small  white  heaps  (Plate  IV.,  Fig.  27).  A  square 
centimetre  of  the  paper,  on  which  were  twenty-six  heaps  of  spores, 
deposited  from  as  many  tubes,  was  then  carefully  cut  out  and 
stirred  up  with  25  cc.  of  water.  The  number  of  spores  in  five 
drops  of  the  mixture  was  then  counted  with  the  Leitz-Wetzlar 
apparatus  and,  from  the  data  thus  obtained,  it  was  calculated  that 
the  number  of  spores  which  had  been  deposited  on  the  square 
centimetre  of  paper  was  44,450,000.  On  the  average,  then,  each 
of  the  twenty-six  tubes  had  produced  1,700,000  spores. 

As  a  control  to  the  above  calculation,  an  estimate  was  made 

1  The  average  length  of  the  spores  in  one  fruit-body  was  found  to  be  12*55  /*. 
Placed  end  to  end,  therefore,  they  would  stretch  through  a  distance  of  forty-one 
miles ! 


84  RESEARCHES   ON  FUNGI 

of  the  number  of  spores  deposited  from  a  single  tube  of  the  fruit- 
body.  It  was  quite  easy  to  cut  out  a  piece  of  paper  bearing  a 
heap  of  spores  of  the  same  size  as  before.  This  was  then  stirred 
up  with  5  cc.  of  water.  As  a  result  of  five  readings  with  the 
counting  apparatus,  the  number  of  spores  was  found  to  be 
1,770,000,  which  is  unexpectedly  near  the  figure  indirectly  obtained 
in  the  previous  calculation.  Since  the  whole  fruit-body  was  some 
250  sq.  cm.  in  area,  the  total  number  of  spores  produced  by  it 


FlG.  35. — Polyporua  squamosus.  Two  fruit-bodies  grown  on  a  log  in  an 
experimental  greenhouse.  (The  early  stages  of  their  development  are 
given  in  Plate  V.,  Figs.  31-34.)  A  considerable  part  of  the  spores  has 
settled  upon  the  log,  giving  it  a  white  appearance.  The  S  was  made 
in  the  spore-deposit  by  rubbing  with  a  finger.  About  £  natural  size. 

would  be  about  the  magnitude  of  11,000,000,000.  The  fruit-body 
in  question,  however,  was  only  one  of  a  group  of  about  ten  upon 
the  same  tree.  The  number  of  spores  produced  by  a  single 
Polyporus  squamosus  plant  growing  in  a  single  tree  in  the  course 
of  a  year,  therefore,  may  exceed  50,000,000,000,  and  probably  in 
some  instances  be  not  less  than  100,000,000,000. 

Daedalea    confragosa. — A    fruit-body,    about    2    square    inches 
in   area,   on   being   revived,1  was   observed   to   shed   a  remarkably 
1  Vide  infra,  Chap.  IX. 


THE   NUMBER  OF  SPORES  85 

dense  cloud  of  spores.  These  were  collected  in  beakers  and  then 
counted.  The  results  given  in  the  Table  indicate  that  the  spores 
were  liberated  most  rapidly  during  the  first  twelve  hours,  and  that 
subsequently  the  rate  of  discharge  gradually  declined.  After  the 
first  week,  spores  continued  to  fall  for  about  three  days  longer, 
but  they  were  evidently  comparatively  few  in  number  and  formed 
but  a  very  thin  spore-deposit.  Their  number  was  not  estimated 
with  the  counting  apparatus.  The  total  output  of  spores  in  the 
laboratory  may  be  taken  as  very  nearly  three-quarters  of  a  billion. 


Area  of  Fruit-body  approximately  2  Square  Inches. 

Time. 

Number  of  Spores. 

Average  Number  of 
Spores  falling 
each  Hour. 

First  12-5  hours. 
Next  24  hours     . 
Next  131-5  hours 

112,300,000 
140,000,000 
429,900,000 

9,000,000 
5,500,000 
330,000 

Totals  :  One  week 

682,200,000 

406,000 

It  may  be  of  interest,  for  the  sake  of  comparison  with  the 
Hymenomycetes,  to  mention  the  results  of  a  determination  of  the 
number  of  spores  produced  by  two  fungi  belonging  to  other  groups 
of  Basidiomycetes.  As  an  average  of  ten  trials  with  the  counting 
apparatus,  the  number  of  spores  contained  within  a  single  smut- 
ball  of  Tilletia  caries,  developed  on  Wheat,  was  found  to  be 
12,125,000.  The  Mushroom  mentioned  above,  therefore,  produced 
as  many  spores  as  one  hundred  smut-balls.  But  numerous  as 
are  the  reproductive  bodies  of  a  Mushroom,  a  Coprinus  comatus, 
or  a  Polyporus  squamosus,  they  pale  into  insignificance  compared 
with  those  produced  by  Lycoperdon  bovista,  Linn.  (L.  giganteum, 
Hussey),  the  Giant  Puff-ball.  A  large,  dry  fruit-body  of  this  fungus, 
collected  by  Dr.  Wright  Wilson  and  given  to  the  University  of 
Birmingham,  was  found  to  be  40  cm.  long,  28  cm.  broad,  and 
20  cm.  high.  Its  weight  was  232  grams.  The  peridium  was 
removed  in  one  place  and  O'l  gram  of  the  internal,  intact  gleba 
carefully  taken  out  with  forceps  and  weighed.  To  this  small 
portion  of  the  fruit-body  250  cc.  of  methylated  spirit  were  added. 


86  RESEARCHES   ON  FUNGI 

Upon  being  stirred,  the  spores  became  evenly  scattered  in  the 
fluid.  With  the  counting  apparatus,  as  an  average  of  several 
trials,  the  O'l  gram  of  the  fruit-body  was  calculated  to  contain 
3,245,000,000  spores.  The  whole  fruit-body,  therefore,  was  calcu- 
lated to  contain  7,500,000,000,000  spores.  The  fruit-body  had  a 
small  sterile  base  and  a  very  thin,  although  imperfect,  peridium, 
but  a  small  part  of  the  gleba  had  been  lost  by  accident.  Taking 
these  factors  into  account,  it  seems  fairly  safe  to  state  that  the 
puff-ball  produced  about  7,000,000,000,000  spores,  or  as  many  as 
would  be  liberated  by  about  4000  good-sized  Mushrooms.  Pro- 
bably a  large  Giant  Puff-ball  which,  it  is  said,  may  sometimes 
almost  attain  the  dimensions  of  a  sheep,  is  the  most  prolific 
organism  living  on  our  planet. 

The  foregoing  figures  will  give  some  idea  of  the  extraordinary 
activity  of  a  large  hymenomycetous  fruit-body  in  producing  and 
liberating  spores.  It  is  safe  to  say  that  a  large  Mushroom, 
Coprinus  comatus  or  Polyporus  squamosus,  liberates  at  least  a 
million  spores  a  minute,  and  keeps  up  this  enormous  rate  of 
discharge  for  several  hours  or  days. 

Since  it  may  be  assumed  that  the  number  of  fruit-bodies  of 
any  given  species  remains  fairly  constant  from  year  to  year,  from 
the  foregoing  figures  we  can  obtain  a  rough  estimate  for  the 
rate  of  elimination  of  the  spores  or  young  plants  by  death.  If 
from  the  spores  of  a  Mushroom  of  Psalliota  campestris  only  one 
Mushroom  were  eventually  produced  on  the  average,  then,  in 
accordance  with  the  figures  obtained,  it  could  be  stated  that 
only  one  spore  in  about  1,800,000,000  ever  manages  to  develop 
into  a  mature  plant.  However,  it  must  be  remembered  that 
each  spore  may  produce  a  wide-spreading  mycelium  or  spawn, 
and  that  this  may  give  rise  to  a  number  of  fruit-bodies.  Doubt- 
less also,  in  nature,  the  spawn  is  perennial  and  often  lives  for 
several  years  in  turf,  &c.,  so  that  a  plant  which  has  arisen  from 
a  single  spore  must  often  produce  a  crop  of  Mushrooms 
annually.  If,  in  consideration  of  these  facts,  we  assume  that, 
when  a  plant  succeeds  in  producing  fruit-bodies  at  all,  it 
produces  altogether  on  the  average  ten  of  them,  it  may  be 
estimated  that  only  one  spore  out  of  about  20,000,000,000  spores 


THE   NUMBER   OF  SPORES  87 

ever  succeeds  in  producing  a  Mushroom  plant  capable  of  repro- 
duction. 

Since  a  single  large  Coprinus  comatus  fruit-body  has  been 
shown  to  produce  about  5,000,000,000  spores,  and  since  the  fruit- 
bodies  often  occur  in  dense  clusters  together,  and  further,  since 
the  mycelium  in  turf  is  possibly  perennial,  it  seems  probable  that 
successful  spores  do  not  number  more  than  one  in  20,000,000,000 
in  this  case  also.  This  may  well  be  an  under-estiinate.  For  the 
perennial  Polyporus  squamosus,  which  produces  fruit-bodies  from 
the  same  tree,  often  year  after  year  for  several  years,  it  has  been 
shown  that  in  one  case  about  100,000,000,000  spores  were  produced 
from  the  fruit-bodies  of  one  plant  in  a  single  year.  Since  making 
this  calculation,  I  have  found  that  large  fruit-bodies  of  Polyporus 
squamosus  shed  their  spores  continuously  for  a  period  of  two  or 
three  weeks.  When  collecting  the  spores  on  the  brown  paper 
for  the  purpose  of  estimating  their  number,  the  fruit-body  was 
only  allowed  to  remain  in  position  for  about  two  or  three  days, 
for  I  then  thought  that  spore-liberation  would  be  at  an  end. 
Hence  it  seems  that  I  have  rather  under-estimated  than  over- 
estimated the  number  of  spores  produced.  Taking  this  into 
consideration,  and  also  the  perennial  character  of  the  plants, 
each  of  which  may  penetrate  through  a  tree  trunk  and  produce 
clumps  of  fruit-bodies  upon  it  in  various  places,  it  seems  to 
me  that  for  every  spore  which  succeeds  in  developing  into  a 
mature  plant  producing  reproductive  bodies,  something  like 
1,000,000,000,000  spores  are  wasted.  How  slight  must  be  the 
chances  for  any  given  spore  of  Polyporus  squamosus  finding  a 
suitable  substratum  for  successful  development! 

Of  thirteen  kinds  of  fish  investigated  by  F.  W.  Fulton,1  the 
ling  proved  to  be  by  far  the  most  prolific  in  producing  eggs.  A 
large  specimen  of  this  species,  61  inches  long  and  weighing  54  Ibs., 
was  found  to  possess  a  roe  containing  28,361,000  eggs.  Doubtless 
this  represented  one  year's  output  in  spawn.  Supposing  that 
the  probable  length  of  life  of  a  spawn-producing  ling  is  as  much 
as  twenty  years,  the  individual  under  discussion  might  altogether 

1  "  The  Comparative  Fecundity  of  Sea  Fishes,"  Ninth  Ann.  Rep.  Fishery  Board 
for  Scotland,  1890.  Quoted  from  Cunningham's  Marketable  Marine  Fishes,  1896. 


88  RESEARCHES  ON  FUNGI 

have  liberated  some  500.000,000  eggs.  Of  course,  only  a  fraction 
of  these  would  have  been  fertilised  and  rendered  capable  of 
developing  into  adult  ling.  We  have  seen  that  a  single  fruit- 
body  of  Psalliota  campestris  produced  1,800,000,000  spores,  one 
of  Coprinus  comatus  5,000,000,000,  and  one  of  Polyporus  squa- 
inosus  11,000,000,000,  and  that  each  fungus  plant  has  a  perennial 
existence  and  may  produce  several  fruit-bodies  each  year.  Hence, 
we  may  conclude  that  these  fungi  are  vastly  more  prolific  in 
the  production  of  cells  capable  of  reproducing  their  species  than 
even  the  most  prolific  kind  of  fish.  The  danger  of  going  astray 
and  dying  of  starvation  or  other  accident  appears,  therefore,  to 
be  even  greater  in  the  case  of  a  fungus  spore,  when  entrusted  to 
the  sportive  winds,  than  in  that  of  a  fish's  egg  when  set  free  in 
sea-water  and  left  to  the  mercy  of  its  currents. 

Bower *  has  calculated  that  the  output  of  spores  of  a  strong  plant 
of  Nephrodium  Filix-mas  in  a  single  season  approaches  50,000,000. 
On  the  other  hand,  as  we  have  seen,  a  single  large  fruit- body  of 
Polyporus  squamosus  produces  at  least  10,000,000,000  spores.  We 
may  conclude,  therefore,  that  the  fungus  is  vastly  more  prolific  than 
the  fern. 

1  F.  O.  Bower,  The  Origin  of  a  Land  Flora,  London,  1908,  p.  23. 


CHAPTER   VI 

MACROSCOPIC   OBSERVATIONS  ON  THE   FALL  OF  SPORES  OF 

POLYPORUS  SQUAMOSUS 

FROM  the  foregoing  chapter  it  is  clear  that  enormous  numbers  of 
spores  fall  continuously  during  the  spore-fall  period  of  a  large 
hymenomycetous  fruit  -  body.  Nevertheless,  the  spores  are  so 
minute  that,  as  a  rule,  one  cannot  observe  the  spore-clouds  with 
the  unaided  eyes.  If  it  were  not  for  the  exact  investigation  into 
the  matter,  it  would  be  difficult  to  believe,  when  one  holds  up  a 
large  ripe  Mushroom,  that,  before  one's  very  eyes  but  yet  unseen, 
a  million  spores  fall  from  the  gills  each  minute.  However,  a 
visible  spore-discharge  has  occasionally  been  observed  as  a  rare 
phenomenon.  Thus  Hoffman1  has  recorded  having  seen  spore- 
clouds  leaving  the  under  surface  of  Polyporus  destructor,  whilst 
Hammer2  has  more  recently  observed  tiny  wreaths  of  spores 
ascending  to  a  height  of  2  or  3  feet  from  a  fruit  -  body  of 
Pleurotus  ostreatus  placed  upon  a  table.  Hermann  von  Schrenk  3 
states  that  from  a  fruit-body  of  Polyporus  Schweinitzii,  "  the 
spores  came  oft'  at  intervals  as  if  they  were  being  discharged 
by  some  force  acting  within  the  tubes."  It  may  be  remarked 
that,  from  numerous  observations  of  my  own  made  by  the  beam- 
of-light  and  other  methods4  on  various  species  of  Polyporese, 
there  seems  to  me  to  be  no  doubt  that  the  spores  which  von 
Schrenk  observed  were  falling  continuously  and  regularly  by  their 
own  weight,  and  that  the  intermittent  clouds  were  caused  by 
tiny,  irregular  air-currents  which  swept  the  spores  along  beneath 

1  Hoffman,  Jahrb.fur  wiss.  Pot.,  Bd.  II.,  1860. 

2  Hammer,  "A  Note  on  the  Discharge  of  Spores  of  Pleurotus ostreatit*"  Torreya, 
V.,  1905,  p.  146. 

3  H.  von  Schrenk,  "Some  Diseases  of  New 'England  Conifers,"  Bull  25,  U.S. 
Dep.  of  Agric.,  1900,  p.  22. 

*  Vide  infra,  Chap.  VII. 


90  RESEARCHES   ON  FUNGI 

the  fruit-body  at  intervals  in  much  the  same  manner  as  steam  is 
swept  by  air-currents  from  the  surface  of  hot  water. 

In  the  month  of  July,  1905,  I  was  fortunately  enabled  to  make 
direct  observations  upon  the  falling  of  the  spores  from  the  fruit- 
bodies  of  Polyporus  squamosus.  My  attention  was  first  called  to 
this  matter  by  Mr.  C.  Lowe,  the  laboratory  attendant.  A  log, 
producing  fruit-bodies  of  the  fungus,  had  been  placed  in  the 
experimental  greenhouse  at  the  Birmingham  Botanical  Gardens. 
Going  into  the  greenhouse  one  morning,  it  appeared  to  Mr.  Lowe 
that  some  one  had  been  smoking  there.  On  looking  round  he 
observed  that  the  "  smoke "  was  coming  from  the  underside  of 
a  freshly -grown  fruit-body  which  was  some  10  inches  in  diameter. 
From  that  morning  onward  until  the  thirteenth  day,  every  time 
the  greenhouse  was  entered  (morning,  afternoon,  and  as  late  as 
nine  o'clock  in  the  evening),  the  clouds  of  spores  were  observed 
coming  off  from  the  fungus.  On  the  thirteenth  day  the  clouds 
were  very  feeble  at  nine  o'clock  in  the  morning  and  ceased  to  be 
visible  about  an  hour  later.  Black  paper  was  then  placed  under 
the  fruit-body  and  on  this  the  white  spores  collected.  By  changing 
the  paper  at  intervals,  I  was  able  to  satisfy  myself  that  the  spores 
continued  to  fall  in  fairly  large  quantities  for  three  days  more.  The 
black  paper  was  whitened  by  the  spores,  but  only  very  feebly  on 
the  last  day.  Altogether,  therefore,  these  observations  proved  that 
the  spores  had  been  falling  continuously  for  sixteen  days. 

The  clouds  of  spores,  which  were  watched  by  the  hour  against 
a  black  background,  resembled  the  steam  coming  off  a  cup  of  tea 
or  the  finest  tobacco  smoke.  The  wreaths  and  curls  of  spores 
appeared  to  originate  in  eddies  made  by  air-currents  in  passing 
over  the  hymenial  surface.  Tapping  the  fruit-body  so  as  to  make 
it  tremble  did  not  appreciably  increase  or  diminish  the  clouds 
of  spores.  The  wreaths  could  be  made  by  artificial  air-currents 
produced  by  movements  of  the  hand  near  the  fruit-body.  Some 
of  the  wreaths  could  still  be  seen  after  they  had  floated  away  to 
a  distance  of  two  yards.  The  clouds  were  distinctly  visible  on  a 
black  background  when  they  were  observed  at  a  distance  of  ten 
yards  from  the  fruit-body. 

The  log  upon  which  the  fruit-body  was  growing  was  watered 


MACROSCOPIC  OBSERVATIONS  91 

from  time  to  time,  but  the  air  of  the  greenhouse  was  dry.  It 
seemed  of  interest  to  find  out  whether  or  not  moist  air  causes  a 
diminution  in  the  rate  of  spore-fall.  Accordingly,  the  log  was 
removed  to  the  Hymenophyllum  house  after  this  had  been  so 
well  syringed  that  its  warm  atmosphere  appeared  to  be  saturated 
with  moisture.  The  spores,  however,  continued  to  fall  for  two 
hours  quite  as  rapidly  as  in  the  dry  greenhouse.  Wreaths  and 
curls  of  spores  floated  slowly  away  from  the  fruit-body.  The 
log  was  then  taken  back  to  its  former  dry  situation,  where  the 
visible  fall  of  spores  went  on  unabated.  Ordinary  variations  in 


FlG.  36. — Spores  leaving  a  fruit-body  of  Polyporus  squamosus  and  being  carried 
away  by  slow  air  movements.     £  natural  size. 

the  hygroscopic  state  of  the  atmosphere,  therefore,  do  not  appear 
to  affect  appreciably  the  fall  of  the  spores. 

Some  very  young  fruit-bodies  which  just  showed  the  earliest 
indications  of  the  development  of  hymenial  tubes  were  found 
growing  upon  a  log  of  wood  in  the  open.  The  log  was  immediately 
removed  and  placed  in  a  dark  room.  Under  these  conditions 
the  hymenial  tubes  developed  in  a  normal  manner  (cf.  Figs.  5,  6, 
and  7,  pp.  29,  32,  and  33),  and  on  the  fourth  day  abundant  spore- 
clouds  were  produced.  These  continued  to  fall  for  eleven  days, 
at  the  end  of  which  time  the  fruit-body  had  begun  to  wither. 
The  production  and  liberation  of  spores,  therefore,  appear  to  be 
carried  on  quite  independently  of  light. 

The  hymenial  tubes  begin  their  development  as  saucer-shaped 
structures  on  the  underside  of  the  pileus.  The  walls  of  the  tubes, 
which  are  positively  geotropic,  then  grow  vertically  downwards 
for  some  days.  By  elongating  in  this  manner,  the  tubes,  although 
often  shorter,  may  attain  a  length  of  a  centimetre  (Fig.  7,  p.  33). 


92  RESEARCHES  ON  FUNGI 

Their  polygonal  pores  are  shown  in  Fig.  6,  p.  32.  By  making 
suitable  sections  and  using  the  microscope,  it  was  found  that  ripe 
spores  were  being  discharged  when  the  tubes  on  a  young  fruit- 
body  were  only  1  mm.  long.  These  observations  lead  me  to  suppose 
that,  in  the  case  of  the  fruit-body  for  which  it  was  found  that  the 
spore-fall  period  lasted  sixteen  days,  spore-emission  had  already 
been  in  process  for  about  a  week  before  the  spore-clouds  were  dis- 
covered. Probably,  therefore,  in  that  instance  the  total  spore-fall 
period  extended  over  about  three  weeks. 

By  placing  black  paper  beneath  a  ripe  fruit-body  for  the  purpose 
of  collecting  the  spores,  it  may  easily  be  proved  that  each  tube 
emits  spores  continuously  for  several  days.  It  may  also  be  shown 
that,  except  for  a  small  zone  about  1  mm.  high  at  the  mouth  where 
no  spores  are  developed,  every  part  of  a  tube  produces  spores. 
A  very  large  fruit-body,  '2  ft.  2  in.  across,  was  gathered  from  a 
tree  and  a  vertical  section  made  through  the  pileus  (Fig.  7,  p.  33). 
The  section  was  placed  on  black  paper.  In  twenty-four  hours  each 
half-tube  had  produced  a  spore-deposit.  The  tubes  were  on  the 
average  about  9  mm.  long,  and  the  spore-deposits,  which  were  of 
an  even  character,  8  mm.  long,  spores  not  having  been  produced 
by  a  zone  round  the  tube  mouths.  A  photographic  reproduction 
of  the  deposits  is  shown  in  Plate  IV.,  Fig.  28 ;  and  Plate  IV.,  Fig.  27, 
gives  a  spore-deposit  collected  from  the  mouths  of  hymenial  tubes 
disposed  on  a  square  inch  of  the  pileus.  We  may  draw  the  con- 
clusion from  these  macroscopic  observations  that  each  hymenial 
tube  during  its  development  liberates  spores  for  several  days  from 
every  part  of  its  spore-producing  surface. 

The  chief  reason  why  one  can  see  the  clouds  of  spores  so  easily 
in  Polyporus  squamosus  is  that  the  spores  come  off  from  the  fruit- 
bodies  in  such  vast  numbers.  In  one  case,  as  already  stated,  a 
single  square  centimetre  of  a  fruit-body  produced  at  the  very  least 
44,450,000  spores  in  two  or  three  days.  A  spore-cloud  resembles 
a  steam  cloud :  the  whole  becomes  visible  owing  to  the  vast  number 
of  the  microscopic  constituent  particles.  The  spores,  too,  are  com- 
paratively large  (14'6x5*13  /A)  and  also  colourless.  They  absorb 
very  little  of  the  light  falling  upon  them,  but  reflect  and  refract 
most  of  it,  so  that  they  glisten.  Like  all  other  particles,  the  spores 


MACROSCOPIC   OBSERVATIONS  93 

fall  by  their  own  weight  in  the  air.  Since  the  rate  of  fall  in  quite 
still  air  is  uniform  and  only  about  1  min.  per  second,1  whilst  air- 
currents  and  convection  currents  beneath  the  fruit-bodies  have 
proportionately  a  much  greater  speed,  which  amounts,  even  in  a 
quiet  greenhouse,  to  several  feet  per  minute,  it  is  not  astonishing 
that  the  spore-clouds  appear  to  float  away  from  the  fruit-bodies 
as  if  they  were  not  sinking  at  all. 

1  Vide  infra,  Chaps.  XV.  and  XVI. 


CHAPTER    VII 

THE   DEMONSTRATION  OF  THE   FALL  OF  SPORES  BY  MEANS 
OF  A   BEAM   OF   LIGHT 

AFTER  I  had  made  the  observations  upon  Polyporus  squamosus 
which  have  just  been  described,  it  occurred  to  me  that  it  might 
be  possible  to  see  the  clouds  of  spores  falling  from  any  hymeno- 
mycetous  fungus  with  the  aid  of  a  sufficiently  strong  beam  of 
light.  Accordingly,  a  large  Horse-mushroom  (Psalliota  arvensis) 
was  obtained  and  placed  as  a  cap  on  an  open  glass  box.  The  light 
from  an  electric  arc  was  allowed  to  pass  through  a  small  hole  in 
a  dark  screen,  and  the  rays  were  then  collected  and  turned  into 
a  strong  parallel  beam  by  means  of  a  biconvex  lens.  The  beam 
was  then  directed  so  that  it  passed  through  the  glass  box.  At  once 
a  very  striking  and  remarkable  result  made  itself  apparent.  On 
looking  at  the  beam  of  light  in  the  box,  one  could  see  the  spores 
floating  in  the  air  in  countless  thousands.  It  seemed  as  if,  in 
miniature,  a  heavy  brown-flaked  snow-storm  was  taking  place. 
Curls  and  wreaths  of  spores,  formed  by  convection  currents,  were 
constantly  proceeding  from  the  gills,  and  the  air  in  the  box  quickly 
became  densely  laden  with  spores.  In  the  course  of  a  few  minutes 
the  density  of  the  spore-cloud  in  the  box  became  constant.  At  this 
stage,  doubtless,  just  as  many  spores  settled  on  the  bottom  of  the 
box  as  were  given  off  at  the  top  by  the  Mushroom  gills.  The 
spores  were  not  to  be  seen  merely  as  clouds.  One  could  clearly 
perceive  any  individual  spore  floating  in  the  light,  and  follow  its 
course  for  some  distance.1  It  has  thus  fallen  to  my  lot,  by  using 
a  very  simple  method,  to  be  the  first  actually  to  observe  the 

1  On  the  same  principle  that  one  can  see  a  star,  although  it  has  no  appreciable 
disc,  or  a  spider's  web  in  strong  sunlight  at  a  distance  of  several  yards.  One  does 
not  perceive  the  dimensions  and  shape  of  a  spore  owing  to  the  insufficient  resolv- 
ing power  of  the  eye.  One  is  simply  aware  that  it  sends  out  light. 


THE   BEAM-OF-LIGHT  METHOD  95 

fascinating  spectacle  of  millions  of  spores  leaving  the  gills  of  a 
Mushroom. 

It  must  not  be  supposed  that  the  ordinary  dust  particles,  which 
are  always  present  in  the  air  in  countless  numbers,  were  mistaken 
for  spores.  With  a  concentrated  beam  of  light  it  is  very  easy  to 
see  the  dust  particles.  In  my  laboratory  they  are  roughly  of  two 
classes:  the  coarser  ones  are  comparatively  rare  and  consist  of 
fibrous  matter,  &c.,  whilst  the  finer  ones  are  extraordinarily 
numerous  and  doubtless  of  the  most  varied  origin.  The  coarser 
particles  alone  can  be  mistaken  for  spores,  but  a  very  little  experience 
is  sufficient  to  prevent  confusion.  These  dust  particles  never 
occur  in  the  form  of  wreaths  or  curls,  and  only  occasionally  float 
into  the  beam  of  light.  Further,  they  are  irregular  in  shape  and 
rarely  affect  the  light  in  the  same  manner  as  a  spore.  The  finer 
particles  are  distinctly  smaller  than  spores,  never  so  regular  in 
size,  and  more  numerous.  They  are  also  somewhat  difficult  to 
see  individually,  for  they  do  not  glisten  in  the  light  nearly  so 
brightly  as  spores.  It  is  evident,  therefore,  that  spores  and  ordinary 
dust  particles  can  be  distinguished  in  a  beam  of  light  with  great 
ease. 

After  finding  that  the  beam-of-light  method  could  be  applied 
with  so  much  success  to  a  Mushroom,  I  made  general  use  of  it  in 
investigating  the  spore-fall  of  a  large  number  of  other  species.  It 
has  proved  of  great  service  in  determining  whether  or  not  spore- 
discharge  was  taking  place  in  any  particular  fruit-body,  in  finding 
out  the  length  of  the  spore-fall  period,  and  in  studying  the  effect  of 
various  external  conditions  upon  spore-liberation. 

It  may  be  stated  quite  generally  that,  whenever  spores  are  falling 
from  a  fruit-body,  they  can  be  observed  with  the  unaided  eye  in  a 
strong  beam  of  light.  So  far  as  my  experience  goes,  there  are  no 
species  of  Hyrnenomycetes  of  which  the  spores  are  too  small  to  be 
seen  in  this  macroscopic  manner.  Even  a  very  slight  discharge  from 
a  fruit-body  may  be  detected.  Sufficient  evidence  of  its  occurrence 
is  provided  by  a  dozen  spores  streaming  through  a  beam. 

It  was  found  convenient  in  my  own  department  to  carry  out 
observations  with  the  beam-of-light  method  in  the  following  manner. 
The  lecture-theatre  lantern,  provided  with  an  electric  arc,  was  set 


96  RESEARCHES   ON  FUNGI 

upon  a  suitable  wooden  stand,  so  that  the  front  lens  was  about  5 
feet  above  the  ground.  To  the  lens  was  attached  a  black  cap,  in  the 
middle  of  which  a  round  aperture,  one  and  a  half  inches  in  diameter, 
had  been  made.  A  bull's-eye  condenser — a  plano-convex  lens 
mounted  upon  a  stand  adjustable  for  any  position,  such  as  is  com- 
monly used  for  illuminating  opaque  objects — was  then  placed  in 
front  of,  and  close  against,  the  aperture  so  that,  when  the  arc  was 
turned  on,  the  condenser  formed  a  concentrated  beam  of  light.  The 
chamber  into  which  the  spores  were  liberated  usually  consisted  of 
a  beaker,  6  inches  high  and  4  in  diameter,  closed  above  by  a 
circular  glass  plate  (Fig.  37).  A  piece  of  sheet  cork  was  fixed  on  to 
the  middle  of  one  side  of  the  plate  by  means  of  sealing-wax.  A 
living  fruit-body,  to  be  tested,  was  pinned  on  to  the  cork  so  that, 
when  the  plate  was  placed  on  the  beaker,  the  fruit-body  had  its  normal 
orientation,  the  hymenial  side  looking  downwards.  The  beaker  was 
then  set  close  in  front  of  the  condenser  in  the  beam  of  light. 

If  a  fruit-body  is  active,  a  stream  of  spores  can  be  detected 
coming  from  it  within  a  few  seconds  after  it  has  been  placed  in 
position  above  the  beam.  The  stream  is  carried  slowly  round  and 
round  in  the  beaker  by  convection  currents.  It  gradually  breaks  up 
so  that  in  a  few  minutes  the  spores  are  well  scattered  (Fig.  37).  A 
maximum  density  of  spores  is  soon  attained.  At  this  stage  as  many 
spores  settle  as  are  liberated.  If  one  directs  the  beam  of  light  so 
that  it  passes  through  the  air  just  beneath  the  gills  or  hymenial 
tubes,  &c.,  one  can  observe  the  spores  slowly  emerging  into  view. 
They  are  then  simply  falling  by  their  own  weight,  at  the  rate,  in 
many  species,  of  1-2  mm.  per  second.1  Convection  currents  sweep 
the  spores,  as  they  emerge  from  the  gills,  hymenial  tubes,  &c.,  slowly 
in  one  direction,  and  it  is  thus  that  a  steady  stream  of  spores  arises. 
The  density  of  the  stream  remains  very  regular  for  hours  or  even 
days.  There  is  no  evidence  whatever  that  the  spores  are  discharged 
intermittently.  The  most  remarkable  thing  about  the  liberation  of 
the  spores  is  just  its  constancy  for  considerable  periods  of  time.  An 
unbroken  stream  of  spores  was  observed  to  be  emitted  from  the  fruit- 
bodies  of  species  of  Polystictus,  Lenzites,  Schizophyllum,  Stereum, 
&c.,  for  days  and  in  some  cases  for  more  than  two  weeks. 
1  Vide  infra,  Chaps.  XV.  and  XVI. 


THE   BEAM-OF-LIGHT  METHOD 


97 


The  spores  of  white-spored  species  stand  out  in  the  beam  of  light 
as  distinct  white   particles,  whilst   the   purple-brown  ones  of  the 


H'.:4 
Pt 


FIG.  37. — Diagram  illustrating  the  discharge  of  spores  from  a 
fruit-body  of  Polystictus  versicolor  as  seen  by  the  beam-of- 
light  method.  The  fruit-body  is  pinned  in  its  natural 
position  to  a  piece  of  cork  attached  to  a  circular  glass 
cover  placed  upon  a  beaker.  A  stream  of  spores  is  carried 
round  within  the  beaker  very  slowly  by  convection  cur- 
rents and  gradually  breaks  up  so  that  the  spores  become 
scattered  fairly  uniformly.  Reduced  to  about  £. 

Mushroom  and  the  black  ones  of  Coprini  present  brownish  and  dull 
metallic  appearances  respectively. 

It  has  been  determined,  by  methods  to  be  explained  subsequently, 
that  very  small  spores,  such  as  those  of  Collybia  dryopkila,  in  still 
air  fall  at  the  rate  of  about  0*5  mm.  per  second,  and  that  the  very 
largest,  such  as  those  of  Coprinus  plicatilis,  fall  at  the  rate  of  about 


98  RESEARCHES   ON  FUNGI 

5  mm.  per  second.  Mushroom  spores  fall  at  a  speed  of  about  1  mm. 
per  second.  It  is  not  surprising,  therefore,  that  convection  currents 
carry  the  spores  round  in  the  beakers  for  a  considerable  time  before 
they  settle  down,  and  that  the  spores  become  spread  fairly  uniformly 
in  the  air  of  any  small  closed  chamber.  In  one  experiment  I  placed 
a  piece  of  a  Mushroom  (Psalliota  campestris)  at  the  top  of  one  end  of 
a  box  which  was  107  cm.  long,  7  mm.  wide,  and  13  cm.  high,  and 
which  was  illuminated  with  a  parallel  beam  of  light  sent  through  it 
lengthwise.  The  spores  were  gradually  scattered  in  the  enclosed  air. 
Some  were  even  carried  to  within  a  few  centimetres  of  the  end  of  the 
box  opposite  to  that  in  which  the  fungus  had  been  placed.  This 
observation  shows  that  very  small  convection  currents  are  capable  of 
carrying  the  spores  over  a  metre  from  a  fruit-body  in  the  lateral 
direction. 

From  observations  which  I  have  made  upon  the  fall  of  spores  in 
glass  chambers  of  various  sizes,  it  seems  that  convection  currents 
are  such  that  the  spores  in  a  sufficiently  large  chamber  (large 
beakers,  &c.)  tend  to  spread  themselves  uniformly  within  its  con- 
tained air,  so  that  equal  numbers  of  them  come  to  occupy  each 
available  unit  of  space.  Richard  Falck l  observed  the  spore-deposits 
made  by  fruit-bodies  placed  in  chambers  provided  with  vertical 
series  of  small  paper  shelves,  and  he  found  that  the  shelves,  even 
when  they  had  been  placed  one  above  the  other  at  short  intervals, 
became  equally  covered  with  spore-dust.  My  own  observations  upon 
falling  spores,  made  by  the  beam-of-light  method,  have  enabled  me 
to  explain  Falck's  results  in  the  following  manner :  Convection 
currents  are  usually  of  such  strength  in  the  chambers  that  the 
spores  are  moved  about  by  them  so  that  equal  numbers  come  to 
occupy  each  unit  of  space.  As  a  result  of  this,  there  is  the  same 
number  of  spores  in  the  layer  of  air  immediately  over  each  shelf. 
As  the  spores  are  falling  by  their  own  weight  at  the  rate  of  about 
1  mm.  per  second,2  a  certain  number  settle  each  second.  Since  the 
conditions  for  the  settling  down  of  spores  over  each  shelf  are 

1 R.  Falck,  "  Die  Sporenverbreitung  bei  den  Basidiomyceten,"  Beitrage  zur 
Biologic  der  Pflanzen,  Bd.  IX.,  1904. 

2  The  rate  varies  according  to  the  species;  c/.  the  Table  of  velocities  in 
Chap.  XV. 


THE   BEAM-OF-LIGHT  METHOD  99 

approximately  the  same,  the  shelves  must  eventually  all  become 
uniformly  covered  with  a  spore-deposit. 

Falck  has  also  called  attention  to  the  fact  that,  when  the  pilei  of 
certain  fungi  are  suspended  in  a  glass  chamber,  one  sometimes 
obtains  curious  and  fantastic  spore-deposits  on  paper  placed  at  the 
bottom  of  the  vessel.  These  irregular  spore-deposits  are  in  my 
opinion  entirely  due  to  the  nature  of  the  convection  currents  in  the 
glass  vessels.  Observations  with  the  beam-of-light  method  have 
taught  me  that,  when  the  velocities  of  the  convection  currents  are 
high  compared  with  the  constant  rate  of  fall  of  the  spores  due  to 
gravity,  the  spores  become  evenly  distributed  in  each  unit  of  space 
in^the  chamber,  and  that  a  uniform  spore-deposit  collects  in  con- 
sequence upon  the  bottom  of  the  chamber,  shelves,  &c.  If,  how- 
ever, the  spores,  such  as  those  of  various  species  of  Coprinus,  are 
large  and  heavy,  and  fall  at  the  rate  of  several  millimetres  per 
second,  and  if,  in  addition,  the  convection  currents  are  not  strong 
compared  with  this  rate  of  fall,  then  we  have  the  conditions 
for  the  formation  of  a  localised  and  irregular  spore-deposit  at 
the  bottom  of  the  chamber.  In  general  it  may  be  stated  that 
the  appearance  of  any  spore-deposit  is  decided  partly  by  the 
speed  and  nature  of  the  movements  of  the  air  through  which 
the  spores  have  fallen,  and  partly  by  the  rate  of  fall  of  the  spores 
themselves. 

The  pileus  of  a  small  Coprinus  fruit-body  which  came  up  on 
horse  dung  and  was  liberating  its  spores,  was  suspended  at  the  top 
of  a  closed  glass  chamber  which  was  about  6  inches  high,  4  inches 
wide,  and  covered  below  with  white  paper.  The  chamber  was  placed 
in  front  of  the  condensing  lens  of  the  lantern.  It  was  observed  that 
a  black  spore-deposit  was  accumulating  on  the  white  paper  along  one 
side  of  the  base  of  the  chamber.  After  about  an  hour  it  was  assumed 
that  the  chamber  had  taken  on  the  room  temperature.  The  arc- 
light  was  suddenly  turned  on,  and  with  the  beam  a  stream  of  spores 
could  be  seen  leaving  the  gills,  falling  obliquely  at  a  rate  of  several 
millimetres  per  second,  and  settling  where  the  spore-deposit  had  been 
accumulating.  Owing  to  the  sides  of  the  vessel  becoming  warmed 
by  heat  accompanying  the  beam  of  light,  new  and  marked  convection 
currents  were  soon  formed.  The  result  was  that  the  stream  of  spores 


ioo  RESEARCHES   ON   FUNGI 

became  deflected  into  a  new  path,  and  the  spores  became  scattered 
fairly  regularly.  In  quite  still  air  in  very  small  chambers,  Coprinus 
spores  fall  quite  vertically.1  These  observations  seem  to  me  to 
warrant  the  belief  that  the  localised  and  irregular  spore-deposit 
formed  by  the  Coprinus  in  the  first  instance  was  due  to  convection 
currents  which  kept  circulating  in  a  constant  path,  thereby  deflecting 
the  rapidly  falling  stream  of  spores  out  of  the  vertical  toward  one 
side  of  the  jar.  It  is  scarcely  necessary  to  discuss  how  regular 
convection  currents  might  arise  in  the  closed  system  which  was 
employed,  but  it  may  be  pointed  out  that  the  living  and  actively 
respiring  Coprinus  pileus  might  well  be  responsible  for  them. 

Falck  arranged  tiers  of  circular  paper  discs,  one  above  the  other, 
in  a  tall  cylindrical  glass  chamber  where  a  pileus  was  liberating 
its  spores.  Under  these  conditions  he  often  obtained  very  curious 
radiating  spore-deposits  on  each  disc.  Here,  again,  the  assumption 
that  convection  currents  taking  regular  paths  existed  in  the 
chamber,  seems  to  me  quite  sufficient  to  give  a  basis  for  an  ex- 
planation of  the  results.  As  one  may  readily  observe  by  means 
of  the  beam-of-light  method,  the  spores  are  carried  away  from 
the  underside  of  the  pileus  in  the  form  of  a  comparatively  thin, 
dense,  and  continuous  stream.  The  stream  which  reveals  the 
presence  of  convection  currents,  doubtless,  would  be  carried  along 
slowly,  first  over  one  surface,  then  over  another,  dividing  here 
owing  to  this  obstacle,  and  turning  back  there  owing  to  another, 
until  finally  it  would  be  broken  up.  Where  on  any  surface  a 
dense  trail  of  spores  has  accumulated,  it  may  be  assumed  that 
the  spore  stream  took  a  regular  path  just  above.  If  the  convection 
currents  are  only  fairly  constant  in  their  directions,  then  owing  to 
the  fact  that  the  spores  in  the  first  instance  are  swept  away  from 
the  pileus  in  the  form  of  a  stream,  fantastic  spore-patterns  seem  to 
be  just  what  should  be  expected  under  the  conditions  provided 
by  Falck's  experiments. 

In  concluding  my  remarks  in  this  chapter,  I  wish  to  recommend 

the  demonstration  of  spore-fall    by  the   beam-of-light   method   to 

all  those  who  give  lectures  or  laboratory  courses  which  include  a 

treatment  of  the  fruit-bodies  of  Hymenomycetes.      It  is  difficult 

1  Vide  infra,  Chap.  XV. 


THE   BEAM-OF-LIGHT  METHOD  101 

for  a  student  to  realise  that  millions  of  spores  are  falling  each 
hour  from  a  ripe  Mushroom  before  his  or  her  very  eyes,  and  yet 
unseen.  A  single  demonstration  of  the  kind  that  I  have  described 
is  likely  to  impress  the  fact  indelibly  on  the  memory.  The  demon- 
stration can  be  carried  out  on  any  day  in  the  year,  even  in  the 
depth  of  winter.  Subsequently,  it  will  be  shown  that  there  are 
many  species  belonging  to  the  genera  Lenzites,  Polystictus,  &c., 
which  can  be  kept  dry  in  bottles  for  months  or  even  years,  and 
which  yet  shed  spores  again  for  days  after  they  have  been  revived 
by  being  placed  for  about  six  hours  under  moist  conditions.  A 
stock  of  such  fruit-bodies  may  be  kept  in  the  laboratory,  and 
revived  at  any  time  with  great  ease  and  certainty  by  placing  wet 
cotton-wool  on  the  pilei.  Instead  of  a  strong  artificial  beam  of 
light,  sunlight,  let  through  a  slit  in  a  dark  room,  is  equally  effective 
for  the  purpose  of  illumination. 


CHAPTER    VIII 

THE   SPORE-FALL  PERIOD 

THE  spores  of  a  hymenomycetous  fruit-body,  under  favourable 
conditions,  are  liberated  continuously  at  a  fairly  constant  rate. 
They  are  never  all  discharged  simultaneously  or  set  free  in  inter- 
mittent showers.  The  falling  spores  may  be  compared  to  raindrops 
steadily  falling  from  the  clouds  on  a  wet  day.  The  process  of 
spore-discharge  often  requires  a  considerable  period  of  time.  This 
may  be  conveniently  called  the  spore-fall  period. 

In  any  given  fruit-body,  the  spore-fall  period  varies  in  length 
according  to  the  rate  of  development  of  the  spores.  This  depends 
on  internal  organisation  and  also  upon  external  conditions,  more 
particularly  of  temperature.  For  many  corky  or  leathery  fruit- 
bodies,  such  as  those  of  Lenzites,  Polys tictus,  Stereum,  &c., 
which  readily  become  dried  up  in  a  dry  atmosphere  and 
quickly  absorb  free  water  through  the  upper  surfaces  of  their 
pilei,  rainfall  and  dew  formation  are  distinctly  favourable  to 
the  discharge  of  spores,  whilst  drought  must  often  temporarily 
interrupt  it. 

It  has  already  been  recorded1  that  a  large  specimen  of  Poly- 
porus  squamosus,  growing  on  a  log,  was  observed  to  shed  its  spores 
continuously  for  sixteen  days.  Reasons  were  also  given  for  sup- 
posing that  in  this  case  the  spore-fall  period  must  have  extended 
over  at  least  three  weeks. 

The  length  of  the  spore-fall  period  was  determined  for  a  number 
of  xerophytic  fruit-bodies  by  means  of  the  beam-of-light  method. 
The  fruit-bodies  which  had  been  detached  from  the  substrata  and 
allowed  to  dry  up  were  revived  in  a  damp-chamber,  suspended 
in  beakers,  and  examined  usually  several  times  a  day  with  a  beam 
from  an  arc-light.  The  beakers  were  kept  in  a  well-heated  labora- 

1  Chap.  VI. 


THE   SPORE-FALL  PERIOD  103 

tory.  Moisture  was  supplied  to  each  fruit-body  by  means  of  wet 
cotton  wool  placed  on  the  upper  surface. 

An  apparently  full-sized  fruit-body  of  Schizophyllum  commune, 
less  than  a  square  inch  in  area,  shed  its  spores  for  sixteen  days 
continuously.  The  density  of  the  spore-stream  leaving  the  gills 
seemed  to  remain  almost  constant  from  a  few  hours  after  its 
formation  onwards,  until  about  three  days  before  the  end  of  the 
spore-fall  period,  when  it  began  to  grow  distinctly  feebler. 

A  small  fruit-body  of  Polystictus  versicolor  shed  spores  for 
sixteen  days,  and  one  of  P.  hirsutus  for  five  days.  A  large 
specimen  of  Lenzites  betulina  gave  a  copious  shower  for  ten  days. 
A  number  of  other  fruit-bodies,  such  as  those  of  Stereum  hirsutum, 
S.  purpureum,  Dsedalea  unicolor,  Merulius  corium,  &c.,  were  seen 
to  discharge  their  spores  for  several  days.  A  complete  investi- 
gation into  the  spore-fall  period  in  all  these  species,  doubtless, 
would  add  much  to  its  length.  In  order  to  carry  it  out,  it  would 
be  necessary  to  examine  a  fruit-body  growing  upon  its  substratum 
from  the  time  it  begins  to  develop  its  hymenium  onwards.  It 
has  already  been  found  that  a  very  young  fruit-body  of  Polystictus 
hirsutus,  grown  in  the  laboratory  on  a  stick,  began  to  shed  a  few 
spores  when  its  hymenial  tubes  had  only  attained  the  size  of 
hemispherical  depressions.  From  this  observation,  and  also  from 
the  fact  that  both  small  and  large  fruit-bodies  of  Schizophyllum, 
Lenzites,  Polystictus,  &c.,  liberate  spores  when  kept  moist,  it  seems 
probable  that  spore-fall  takes  place  in  species  belonging  to  these 
genera  in  a  manner  similar  to  that  exhibited  by  Polyporus  squamosus, 
i.e.  the  discharge  of  spores  begins  soon  after  the  fruit-bodies  have 
expanded  horizontally,  when  the  hymenium  begins  its  development, 
and  continues  until  the  pilei  Have  grown  to  their  full  extent.  This 
may  be  in  some  cases  a  matter  of  days,  in  others  certainly  of  weeks, 
or  in  yet  others  possibly  of  months. 

For  Psalliota  campestris  and  allied  fruit-bodies  spore-fall  does 
not  begin  until  the  pileus  has  expanded  and  the  gills  have  become 
more  or  less  horizontally  outstretched.  By  placing  paper  close 
beneath  the  pilei  of  some  Mushrooms  growing  on  an  artificial  bed, 
and  thus  collecting  the  spores,  it  was  found  that  the  spore-fall 
period  continued  for  two  or  three  days. 


io4  RESEARCHES  ON  FUNGI 

A  fully  expanded  fruit-body  of  Pleurotus  ulmarius,  when 
confined  in  a  large  beaker  in  the  laboratory,  was  observed  by  the 
beam-of-light  method  to  shed  spores  for  seventeen  days  continu- 
ously. During  the  last  few  days  the  gills  gradually  turned  mouldy. 
Since  the  fruit-body  appeared  to  be  of  full  size  and  expansion  when 
gathered,  it  seems  probable  that,  had  it  been  left  to  continue  its 
existence  under  natural  conditions,  its  spore-fall  period  might  have 
exceeded  three  weeks. 

Coprinus  comatus  sheds  spores  from  the  moment  "deliquescence" 
begins  at  the  base  of  the  gills  until  these  have  disappeared.  For 
some  large  specimens,  growing  in  a  field  under  favourable  weather 
conditions,  the  spore-fall  period  was  found  to  last  about  two  days 
and  two  nights.  Smaller  species  of  Coprinus,  such  as  C.  plicatilis, 
shed  their  spores  in  a  few  hours. 

The  continuous  discharge  of  spores  for  days  or  weeks  is  certainly 
a  remarkable  fact  which  requires  further  elucidation  from  the  point 
of  view  of  development.  It  must  be  remembered  in  this  connection 
that  adjacent  basidia  in  most  fruit-bodies  are  in  very  various  stages 
in  regard  to  the  production  of  spores.  The  fact  that  after  the  spores 
on  a  basidium  have  attained  their  full  size  and  final  colour,  they 
remain  on  the  sterigmata  but  a  very  short  time,  seems  to  show  that 
they  are  discharged  as  soon  as  ripe.  There  must  be  some  means  by 
which  a  succession  of  developing  basidia  on  any  given  part  of  the 
hymenium  is  provided.  Possibly  the  discharge  of  spores  from  one 
basidium  serves  as  a  stimulus  for  the  development  of  one  or  more 
neighbouring  basidia.  It  is  certain,  however,  that  the  process  is 
beautifully  regulated,  for  thus  only  could  a  Polyporus  squamosus, 
a  Lenzites  betulina,  or  a  Polystictus  versicolor  give  out  millions  of 
spores  in  such  steady  streams  for  many  days  without  interruption. 


CHAPTER     IX 

DESICCATION   OF   FRUIT-BODIES— A  XEROPHYTIC   FUNGUS 
FLORA— THE  GENUS  SCHIZOPHYLLUM 

HITHERTO  the  retention  of  vitality  by  fruit-bodies  after  desiccation 
does  not  appear  to  have  been  thoroughly  investigated.  In  systematic 
works  on  fungi,  it  is  stated  that  fruit-bodies  in  the  genera  Marasmius 
and  Collybia  revive  after  .being  dried  up  when  they  obtain  access  to 
moisture,  but  beyond  this  general  fact  nothing  further  seems  to  have 
found  its  way  into  botanical  literature.  However,  probably  most 
field  mycologists  have  noticed  that  leathery  and  corky  fruit-bodies 
occurring  on  sticks  and  logs  of  wood  become  freshened  up  in  rainy 
weather. 

A  test  for  retention  of  vitality  is  not  afforded  by  the  fact  that  a 
dried  fruit-body,  when  viewed  macroscopically,  apparently  regains  its 
turgidity  on  access  to  moisture,  for  a  number  of 'dead  fruit-bodies 
swell  up  in  this  way,  e.g.  Lenzites  betulina.  The  swelling  in  this  and 
many  other  species  is  simply  due  to  the  expansion  of  the  hyphal 
walls.  A  slow  oxydative  change  going  on  in  a  dried  fruit-body 
would  also  be  an  unreliable  test  for  retention  of  vitality,  for  Paul 
Becquerel 1  has  shown  that  seeds  which  were  killed  by  heating  and 
then  dried,  "  respired  "  more  actively  than  dried  seeds  still  capable  of 
germination.  If,  however,  when  supplied  with  moisture,  a  fruit-body 
again  begins  to  shed  spores,  then  we  have  a  clear  and  convincing 
proof  that  it  is  still  living.  A  fruit-body  which  has  been  killed 
never  sheds  any  spores.  Even  when  a  fruit-body  which  is  actively 
discharging  spores  is  placed  under  the  influence  of  ether  vapour,2 
spore-fall  ceases  immediately.  The  liberation  of  spores,  therefore,  is 
an  active  process,  the  carrying  out  of  which  may  be  taken  as  sure 
evidence  that  the  fungus  concerned  is  still  living. 

1  P.  Becquerel,  "  Sur  la  nature  de  la  vie  latente  des  grains  et  sur  les  veritable 
charactores  de  la  vie,"  Comptes  Rendus,  T.  143,  1906,  p.  1177. 

2  Vide  infra,  Chap.  X. 

105 


106  RESEARCHES  ON  FUNGI 

Experience  has  shown  that  spores  which  have  just  been  liberated 
always  have  a  fresh  and  turgid  appearance  when  observed  in  water. 
They  give  one  the  impression  that  they  are  capable  of  germination. 
That  spores,  newly  shed  from  a  fruit-body  which  previously  has  been 
kept  desiccated  for  a  long  period,  may  germinate  readily  under 
suitable  conditions,  has  been  proved  for  the  only  two  species  so  far 
tested,  namely,  Dtedalea  unicolor  and  Schizophyllum  commune.  A 
fruit-body  of  the  former  species  was  kept  dry  for  three  years,  and  one 
of  the  latter  for  one  year.  They  both  recovered  when  wet  cotton 
wool  was  placed  on  their  upper  surfaces.  Spores 
liberated  within  ten  hours  after  the  fruit-bodies 
had  been  moistened  germinated  readily  within 
a  further  twenty-four  hours  in  hanging  drops 
of  a  nutrient  medium  containing  meat  extract, 
grape-sugar,  peptone,  and  gelatine  (Fig.  38). 
These  observations  seem  to  afford  strong  evidence 
in  favour  of  the  view  that,  whenever  spore-emis- 
sion  is  taking  place  from  a  fruit-body,  the 
emitted  spores  are  living. 
F  were8^ ?rorm'  JvS  Xt  not  ^frequently  happens  that  a  desiccated 
fruit-bodies,  in  course  fruit-body,  separated  from  its  substratum  and 

of     germination    after      ,,  .  .,,.. 

twenty-four  hours  in  a  allowed  access  to  water,  in  addition  to  liberating 
SSltZ:  1'  spores  also  recommences  growth.  Such  growth 
Schizophyllum  commune.  in  species  of  Polyporefe  may  lead  to  a  slight 

Magnification,  700.  J 

elongation  of  the  hymenial  tubes  or  even  to  the 
production  of  very  shallow  new  ones  at  the  edges  of  the  fruit-bodies. 
Renewed  growth  of  this  kind  can  easily  be  detected  macroscopically, 
and  it  has  been  observed  in  Polyporus  rigens,  Polystictus  hirsutus, 
and  Glwoporus  conchoides.  The  fruit-bodies  in  question  had  been 
kept  dry  for  a  year  before  being  moistened. 

Most  succulent  fruit-bodies,  such  as  those  of  species  belonging  to 
the  genera  Psalliota,  Amanita,  Coprinus,  Boletus,  &c.,  are  unable  to 
survive  even  partial  desiccation.  The  Marasmii  are  exceptions  to 
this  rule.  Fruit-bodies  of  Marasmius  oreades  were  gathered  from  a 
"  fairy  ring  "  in  a  field  and,  when  tested  in  the  laboratory,  were  found 
to  be  freely  liberating  spores.  They  were  then  well  dried  by  means 
of  hot  air.  During  the  drying  process  the  fleshy  pileus  became  quite 


DESICCATION   OF   FRUIT-BODIES 


107 


stiff  and  white,  and  the  gills  shrivelled  up  (Fig.  40,  A,  B,  and  C). 
After  the  fruit-bodies  had  been  kept  in  the  dried  state  for  twenty- 
four  hours,  free  water  was  allowed  to  come  into  contact  with  the 
upper  surfaces  of  the  pilei  and  with  the  stipes.  It  was  readily 
absorbed.  The  fruit-bodies  became  swollen,  and  completely  resumed 
their  normal  appearance  in  the  course  of  a  few  hours  (D  and  F). 
At  the  end  of  this  time  they  were  actively  shedding  spores.  Thick 
spore  -  deposits  collected 
beneath  the  pilei  on  black 
paper  (E),  and  the  dis- 
charge of  spores  from  the 
sterigmata  was  watched 
by  means  of  microsco- 
pic sections.  Convincing 
proof  was  thus  obtained 
that  the  fruit-bodies  of 
Marasmius  oreades,  after 
complete  desiccation,  are 
capable  of  reviving  on 
access  to  moisture  and  of 
resuming  their  normal 
activities.  The  retention 
of  vitality  in  the  dried-up 
condition,  however,  is  only 
temporary.  It  was  found 
by  subsequent  experi- 
ment that  fruit  -  bodies 
which  had  been  kept  stiff 
and  hard  were  still  capable  of  recovery  after  six  weeks  but  not 
after  three  months. 

Fruit-bodies  of  Marasmius  peronatus  and  of  Collybia  dryophila 
were  allowed  to  dry  on  a  laboratory  table.  They  were  then  tested  at 
intervals  for  revival.  The  tests  showed  that  recovery  was  possible 
when  the  desiccated  condition  had  lasted  for  only  a  few  days,  but  not 
when  it  was  continued  for  a  month. 

On  hot  days  in  summer  and  early  autumn,  one  not  infrequently 
sees  shrivelled-up  fruit-bodies  of  Marasmius  oreades  in  "  fairy  rings  " 


FIG.  39. — Marasmius  oreades.  To  the  left  a  fruit- 
body  shrivelled  up  during  drought.  To  the  right 
a  fruit-body  which  after  becoming  shrivelled  up 
was  revived  under  moist  conditions  and  is  again 
shedding  spores.  Natural  size. 


io8 


RESEARCHES   ON  FUNGI 


in  meadows  (Fig.  39).  The  fruit-bodies  are  developed  during  a  spell 
of  wet  weather,  but,  when  the  air  and  soil  become  reduced  in 
moisture,  and  especially  when  the  radiation  of  the  sun  is  intense, 
they  slowly  dry  up  and  cease  to  shed  spores.  As  soon  as  rain  comes 
again,  water  is  quickly  reabsorbed  through  the  top  of  the  pileus,  and 
the  spore-liberating  function  is  resumed.  There  can  be  no  doubt 
that  the  revival  of  the  fruit-bodies  of  Marasmii  after  desiccation  is 
an  advantageous  adaptation  which  prevents  a  great  loss  of  spores. 


FlG.  40. — Marasmius  arcades.  A  and  B,  the  under  surfaces,  and  C,  the  upper 
surface  of  the  pilei  of  three  fruit-bodies  after  desiccation.  D  and  F  are  the 
pilei  A  and  C  respectively  three  hours  after  the  commencement  of  revival  by 
absorption  of  water  through  their  upper  surfaces.  E,  a  spore-deposit  from 
the  pileus  D  (A  revived).  Natural  size. 

During  dry  weather  in  early  autumn  I  have  several  times  gathered 
shrivelled-up  specimens  of  Collybia  dryophila  growing  among  leaves 
in  woods.  Upon  being  wetted,  the  pilei  soon  became  fully  expanded 
again,  and  spore-liberation  was  then  actively  resumed.  It  is  evident 
that  the  fruit-bodies  of  Collybia  dryophila  retain  their  vitality  after 
desiccation  in  just  the  same  manner  as  those  of  Marasmius  oreades. 

As  a  result  of  experiments  upon  a  considerable  number  of  typical 
species,  the  names  of  which  will  shortly  be  given  in  a  Table,  it  seems 


A   XEROPHYTIC   FUNGUS   FLORA  109 

safe  to  state  that  very  many,  and  possibly  all,  of  the  small  leathery 
and  corky  fruit-bodies  of  Hymenomycetes  which  are  to  be  found 
developing  on  fallen  logs  and  sticks  in  woods,  are  capable  of  com- 
plete recovery  after  desiccation.  In  a  number  of  instances  they  can 
be  kept  dry  for  months  or  even  for  several  years,  apparently  without 
the  smallest  detriment  to  their  power  of  liberating  spores  after 
absorbing  water  once  more.  Among  the  species  in  question  one  may 
mention  those  belonging  to  the  following  genera :  Schizophyllum, 
Lenzites,  Trogia,  Dsedalea,  Polyporus,  Polystictus,  Merulius,  Phlebia, 
Stereum,  and  Corticium.  These  fungi  must  be  regarded  as  xero- 
phytes,  for  their  fruit-bodies  are  capable  of  withstanding  drought 
by  drying  up  without  any  loss  of  vitality  and  of  reviving  again 
under  moist  conditions. 

Fruit-bodies  of  Lenzites,  Polystictus,  &c.,  which  were  required 
for  testing,  were  gathered  during  October  and  November  from 
stumps,  logs,  and  sticks  in  the  woods  near  Winnipeg,  and  placed 
on  a  table  in  the  laboratory.  There  the  air  was  very  dry,  so  that 
desiccation  took  place  rapidly.  A  dried  fruit-body,  still  living, 
revived  when  it  had  been  set  in  a  damp-chamber  and  wet  cotton- 
wool had  been  placed  on  the  top  of  its  pileus.  It  quickly  absorbed 
the  free  water,  expanded,  and  soon  came  to  have  a  fresh  appear- 
ance. After  a  few  hours  spore-liberation  was  resumed.  This  was 
proved  in  my  first  experiments  by  collecting  spore-deposits  on  paper, 
but  subsequently  this  method  was  discarded  and  the  beam-of-light 
method  used  instead.  It  has  already1  been  made  sufficiently  clear 
that  a  strong  beam  of  light,  directed  beneath  a  fruit-body  in  a  closed 
beaker,  readily  enables  one  to  determine  whether  or  not  spore-fall 
is  taking  place. 

As  a  rule,  only  a  very  few  hours  are  required  for  a  dried-up 
fruit-body  to  regain  its  spore-liberating  function.  A  specimen  of 
Schizophyllum  commune,  kept  dry  for  six  months,  recovered  in 
three  hours.  Merulius  corium  and  Polystictus  versicolor,  kept  dry 
for  six  months,  and  Lenzites  betulina,  kept  dry  for  two  years  and 
six  months,  all  required  about  four  hours  to  recover.  In  other  cases 
it  was  found  that  spore-fall  usually  recommenced  within  six  hours 
after  the  fruit-bodies  had  been  placed  under  moist  conditions.  A 
1  Chap.  VIII. 


no  RESEARCHES   ON  FUNGI 

fruit-body  of  Dtedalea  unicolor,  kept  dry  for  two  years  and  six 
months,  recovered  in  about  four  hours,  but  another  fruit-body  of 
the  same  species,  kept  dry  for  four  years,  recovered  in  about  7*5 
hours.  This  observation  indicates  that  those  fruit-bodies  which 
have  been  kept  longest  in  the  desiccated  condition  are  the  slowest 
to  revive. 

All  the  fruit-bodies  tested  were  found  to  retain  their  vitality 
for  several  months,  some  of  them  for  more  than  two  years,  and  one, 
namely,  Diedalea  unicolor,  for  more  than  four  years.  Only  in  a  few 
species,  owing  to  lack  of  material  old  enough,  has  it  been  possible 
for  me  to  determine  within  what  period  death  occurs.  However, 
the  investigation  seems  to  indicate  that  every  dried  fruit-body 
exposed  to  the  air  loses  its  vitality  in  the  course  of  a  few  months 
or  years,  just  as  does  a  seed.1  In  the  Table  opposite  is  given 
a  list  of  the  fungi  which  were  tested,  and  also  the  results  of  tests 
made  after  various  periods  of  desiccation. 

Some  well-grown  specimens  of  Lenzites  betulina  and  of  Schizo- 
phyllwm  commune  were  collected.  Doubtless,  they  had  already 
shed  an  abundance  of  spores  before  they  were  gathered.  They 
were  kept  dry  for  a  whole  year,  and  then  revived  in  a  damp- 
chamber,  whereupon  they  shed  clouds  of  spores.  Again,  by  drying, 
they  were  put  to  rest  for  another  year,  and  at  the  end  of  this  second 
period  of  desiccation  they  were  again  allowed  access  to  free  water. 
They  revived  and  shed  spores  once  more.  A  similar  revival  was 
found  to  take  place  even  after  desiccation  for  a  third  year,  but  an 
attempt  to  revive  the  fruit-bodies  after  a  fourth  year  of  desiccation 
was  unsuccessful:  the  fruit-bodies  became  discoloured  and  putrid 
without  shedding  any  spores. 

Sticks,  dead  branches,  and  logs  in  woods  are  all  liable  to  become 
dried  up.  When  this  happens  the  mosses,  lichens,  and  fungi  upon 
them  must  gradually  dry  up  too.  It  is  not  surprising,  therefore, 
that  these  plants  are  adapted  to  withstand  temporary  desiccation. 

1  Paul  Becquerel  (loc.  cit.,  p.  1178)  found  that  dried  seeds  of  various  kinds 
placed  in  pure  and  dry  nitrogen  in  the  dark  for  a  year,  did  not  liberate  a  trace 
of  carbon  dioxide,  and  yet  germinated  subsequently.  It  will  be  of  interest  to 
determine  whether  or  not  dried  fruit-bodies  of  fungi  are  also  capable  of  retaining 
their  vitality  without  any  evidence  of  respiratory  activity.  If  life  may  become 
latent  in  dry  seeds,  it  may  also  do  so  in  dried  fruit-bodies. 


A   XEROPHYTIC   FUNGUS   FLORA 


They  survive  through  periods  of  drought  by  drying  up  and  retain- 
ing their  vitality.  The  hyraenomycetous  stick  or  log  flora  is 
therefore  xerophytic. 

While  it  has  now  been  demonstrated  that  many  of  the  fruit- 
bodies  of  wood-destroying  fungi  are  able  to  withstand  desiccation 
unharmed,  the  resistance  of  the  mycelium  to  dry  conditions  still 
requires  an  experimental  investigation.  Quite  possibly  in  some 

List  of  Hyinenomycetes  with  fruit-bodies  which  can  become  Desiccated 
without  losing  their  Vitality. 


Family. 

Species. 

Recovered  after 
Desiccation  lor 

Failed  to  Recover 
after  Desiccation  for 

'    Corticium  laeve 

1  year 

Thelephoreae  - 

Stereum  hirsutum 
,,        purpureum 
„        bicolor 

1  year 
1  year 
1  year  6  months 

1  year  6  months 
2  years 

Hydnese  .     . 

Phlebia  pileata 
„        zonata 

2  years  8  months 
1  year 

4  years  4  months 
3  years  6  months 

Merulius  corium 

2  years 

... 

Gloeoporus  conchoides 

1  year 

Dtedalea  unicolor 

4  years 

... 

„        confragosa 

1  year 

„        quercina 

1  month 

5  years 

Polyporese  .  - 

Polyporus  conchifer 

4  months 

5  months 

„          rigens 

2  years 

„          carneus 

2  years 

... 

Polystictus  versicolor 

2  years 

4  years 

„          hirsutus                      3  years 

... 

„          pergamenus                1  year 

Trogia  crispa                                 4  months 

1  year 

Schizophyllum  commune               2  years 

16  years 

Lenzites  betulina                           3  years 

5  years 

Agaricinese  .  • 

„        ssepiaria 
Crepidotus  sp.  (?) 

4  months 
a  few  weeks 

Marasmius  oreades                         6  weeks 

3  months 

„           peronatus 

a  few  days 

1  month 

Collybia  dryophila                          1  week 

1  month 

cases  the  xerophytism  of  a  fungus  is  only  partial,  so  that  desicca- 
tion is  fatal  to  the  mycelium  but  harmless  to  the  fruit-bodies. 
However,  the  rapidity  with  which  fruit-bodies,  on  the  advent  of 
rain,  develop  upon  sticks  which  have  been  dried  up  for  weeks  in 
summer,  points  to  the  conclusion  that  the  mycelium  in  the  wood 
must  very  frequently  retain  its  vitality  in  a  state  of  desiccation. 
A  somewhat  striking  laboratory  experiment  with  Polystictus  versi- 


ii2  RESEARCHES   ON   FUNGI 

color  lends  considerable  support  to  these  general  field  observations. 
A  stick,  about  4  cm.  thick  and  30  cm.  long,  bearing  a  number  of 
fruit-bodies  of  the  fungus  in  question,  was  gathered  by  myself  and 
kept  in  a  dry  state  as  a  museum  specimen.  After  an  interval  of 
four  years  it  was  found  that  the  fruit-bodies,  on  being  moistened 
in  the  usual  manner,  did  not  shed  any  spores,  but  appeared  to  be 
discoloured  and  to  have  lost  their  vitality.  The  stick  was  then 
given  to  Miss  J.  S.  Bayliss  for  certain  investigations  which  she 
was  then  carrying  on.  It  was  set  in  a  damp-chamber  with  one  end 
in  water.  Four  weeks  later  Miss  Bayliss  observed  that  a  number  of 
new  fruit-bodies  of  Polystictus  versicolor  had  begun  to  develop 
upon  it.  In  the  course  of  a  few  weeks  some  of  them  attained 
considerable  size.1  This  observation  seems  to  me  to  prove  con- 
clusively that  the  mycelium  in  the  wood  must  have  retained  its 
vitality  for  four  years  in  the  desiccated  condition. 

It  is  well  known  that  the  mycelium  of  Psalliota  campestris, 
when  kept  dry  as  "spawn"  in  compressed  horse-dung  bricks,  re- 
tains its  vitality  for  years.  According  to  Falck,2  the  mycelium  of 
Coprinus  sterquilinus  is  still  able  to  continue  its  development  after 
the  horse-dung  balls,  in  which  it  has  existed,  have  been  kept  dry 
for  a  year.  In  both  these  instances  the  vegetative  part  of  the 
fungus  is  resistant  to  desiccation,  whereas  the  reproductive  part 
is  not. 

The  xerophytic,  hymenomycetous  fruit-bodies  growing  on  logs, 
such  as  those  named  in  the  Table,  have  several  features  in 
common.  This  is  only  what  might  be  expected  when  it  is 
remembered  that  they  are  all  adapted  to  the  same  external 
conditions,  i.e.  to  develop  on  a  wooden  substratum  chiefly  in 
the  cool  and  late  autumn  months.  The  points  of  agreement  are 
as  follows  : — 

1.  They  retain  their  vitality  for  months  or  years  after  desiccation. 

2.  They  are  all  firmly  built  and  resemble  in  consistency  leather, 
cork,  or  wood.      Their  toughness  renders  them  inedible  to  slugs 
and  favours  their  persistence  through  periods  of  drought  and  frost. 

1  Miss  J.  S.  Bayliss,  "The  Biology  of  Polystictus  versicolor  (Fries.),"  Journ.  of 
Economic  Biology,  vol.  iii.,  1908,  p.  20. 

2  R.  Falck,  Beitrage  zur  Biologie  der  Pflanzen,  Bd.  VIII.,  1902,  p.  317. 


SCHIZOPHYLLUM   COMMUNE  113 

3.  The  upper  surface  of  the  pileus  is  usually  hairy  or  woolly. 
A   means  is  thus  provided  for  the  rapid  absorption  of  water  on 
the  advent  of  rain.     Free  water  placed  at  one  edge  of  the  pileus 
quickly  passes  by  capillarity  over  the  entire  upper  surface.     Since 
in  many  species  the  fruit-bodies  more  or  less  overlap  one  another, 
this  arrangement  may  be  of  advantage  in  hastening  recovery  after 
desiccation.       The  hairs,  like  those  on  the  leaves  of  certain  xero- 
phytic  Phanerogams,  are  doubtless  of  some  service  in  diminishing 
the  rate  of  transpiration  in  dry  weather.      Direct  evidence  of  this 
is  afforded   by  an   experiment  made  by  Miss  J.  S.  Bayliss,1  who 
found  that  the  removal  of  the  hairs  from  the  upper  surface  of  a 
pileus  of  Polystictus  versicolor  increased   the  rate   at  which   the 
process  of  drying  took  place. 

4.  They  are  able  to  withstand  prolonged  and  severe  frost  (such 
as  occurs  at  Winnipeg). 

5.  They  shed  their  spores  at  low  temperatures.      A  number  of 
them  can  perform  this  function  even  at  0°  C.2 

6.  Their  attachment  is  unilateral.     This  is  connected  with  the 
fact    that    they   grow    on    stumps,    sticks,    and    fallen   logs.     The 
dimidiate  form  of  the  fruit-bodies  is  as  well  adapted  to  the  posi- 
tion of  the  woody  substratum  as  the  radial  form  is  to  the  position 
of  the  earth  in  the  Mushroom  and  Boleti,  &c. 

The  Genus  Schizophyllum.— The  genus  Schizophyllum  is  unique 
among  the  Agaricineae  in  that  it  is  characterised  by  possessing 
gills  which  are  either  partially  or  completely  divided  down  their 
median  planes  into  two  parts.  We  shall  now  proceed  to  interpret 
this  remarkable  morphological  fact  in  the  light  of  observations  made 
upon  Schizophyllum  commune. 

Schizophyllum  commune  is  a  species  comparatively  rare  in 
England  but  extremely  common  in  Manitoba,  where  it  is  found 
on  sticks,  logs,  and  stumps.  The  fruit-bodies,  which  are  usually 
attached  laterally,  attain  a  width  of  about  3  cm.  They  occur 
singly  or,  more  frequently,  in  imbricated  groups.  Their  general 
appearance  is  shown  in  Fig.  41,  A  and  B,  and  Fig.  42.  The  gills 
are  in  distinct  fasciculi,  each  pair  of  deeper  and  longer  ones  being 

1  Miss  J.  S.  Bayliss,  loc.  ««.,  p.  17. 
»  Vide  infra,  Chap.  X. 


ii4  RESEARCHES   ON   FUNGI 

separated  by  from  three  to  five  others  which  are  shallower  and 
shorter   (Fig.  41,  E).      The   upper  layer  of  the   pileus   presents  a 


FlG.  41. — Schizophyllum  commune — a  specialised  xerophyte.  A  and  B,  fruit-bodies 
seen  from  above  growing  on  wood.  Natural  size.  C  and  D,  two  fruit-bodies 
seen  from  below  and  in  section  respectively.  About  twice  natural  size.  B, 
section  through  a  pileus  during  wet  weather  showing  the  gills,  which  are  split 
down  their  median  planes.  F,  section  through  a  pileus  after  desiccation.  E 
and  F  about  12  times  the  natural  size. 


woolly  appearance  and  is  made  up  of  tangled  hyphse  which  extend 
downwards    towards   the   median    planes   of  all   the    deeper    gills. 


SCHIZOPHYLLUM   COMMUNE  115 

The  under  layer  of  the  pileus,  the  firm  flesh  which  is  produced 


FlG.  42.—Schizophyllu»i  commune.  The  lower  photograph  shows  a  group 
of  fruit-bodies  in  the  desiccated  condition.  The  gill-fasciculi  are 
closed  up.  Natural  size.  The  upper  photograph  shows  the  same 
group  of  fruit-bodies  after  being  revived.  The  gill-fasciculi  are  now 
open.  About  $  natural  size. 

downwards  to  form  the  gills,  thus  becomes  divided  into  radiating 
portions  (Fig.  41,  E). 


RESEARCHES   ON   FUNGI 


The  area  of  a  fruit-body  is  increased  by  marginal  growth. 
The  peripheral  walls  of  the  interlamellar  spaces  protrude  outwards 
as  crenatures,  and  more  or  less  resemble  the  heels  of  slippers 
placed  side  by  side  in  a  row  (Fig.  43).  These  crenated  walls 
constitute  growing  regions  by  means  of  which  the  older  gills  are 

lengthened  and  new 
ones  added.  Whilst  a 
pileus  is  extending  by 
marginal  growth,  the 
interlamellar  spaces 
gradually  widen. 
When  a  space  has  at- 
tained a  certain  width, 
it  becomes  divided  into 
two  down  the  middle, 
owing  to  the  formation 
within  it  of  a  new  gill 
which  arises  as  a  short 
median  downgrowth 
from  the  pileus  flesh 
(Fig.  43,  a).  The  upper 
half  of  every  new  gill 
is  undivided,  but  the 
lower  half  is  made  up 
of  two  plates,  the  inner 
surfaces  of  which  are 
in  contact  and  clothed 
with  loose  hyphse  (cf. 


FIG.  43. — Schizophyllum  commune.  Piece  of  a  pileus  seen 
from  below  showing  the  arrangement  of  the  gills. 
a-<7,  stages  in  gill  development;  h.  part  of  the 
woolly  layer  covering  the  top  of  the  pileus  and  here 
extended  over  the  pileus  margin  ;  i,  interlamellar 
space.  Semidiagrammatic:  the  gills  are  represented 
as  cut  through  transversely  so  that  the  surfaces  of 
section  lie  in  one  plane.  About  13  times  the 
natural  size. 


Fig.4LE).  Agill,whilst 
still  very  short,  occu- 
pies an  isolated,  sub- 
terminal  position  within  the  interlamellar  space  in  which  it  has  been 
formed.  However,  as  growth  proceeds,  its  distal  end  gradually 
approaches  the  pileus  margin  and  eventually  joins  with  it 
(Fig.  43,  a-e).  All  gills  at  their  first-formed,  stipe  ends  are 
shallow  and  only  partially  divided.  However,  at  their  peripheral 
growing  ends  they  gradually  become  deeper  and  more  divided, 


SCHIZOPHYLLUM   COMMUNE 


117 


until  at  length  they  come  to  consist  solely  of  two  deep,  apposed 
plates.  After  a  young  gill  has  become  connected  with  the 
pileus  margin,  its  two  plates  separate  from  one  another  slightly 
at  their  peripheral  ends.  This  separation  of  the  gill  plates,  as 
growth  proceeds,  becomes  more  and  more  marked,  and  at  length 
involves  the  pileus  flesh.  The  peripheral  end  of  every  long  and 
deep  gill  thus  comes  to  resemble  in  cross  section  the  deepest 
gills  shown  in  Fig.  41,  E.  The  whole  gill  system  may  be  regarded 
as  being  made  up  of  branched  fasciculi. 

Schizopkyllum  commune,  as  we  have  already  seen,  is  a  xero- 
phyte.  In  moist  weather  the  gills  all  look 
vertically  downwards,  as  in  the  Mushroom, 
and  spore-discharge  takes  place  for  days 
from  their  hymenial  surfaces  (Fig.  41,  E). 
When  dry  weather  comes,  and  the  wooden 
substratum  gradually  loses  its  water,  de- 
siccation of  the  fruit-body  sets  in.  The 
emission  of  spores  soon  ceases,  and  the 
two  halves  of  each  gill  begin  to  diverge 
below  (Fig.  44).  As  desiccation  proceeds, 
the  gill  plates  become  curled  outwards 
at  their  edges.  When  a  fruit-body  has 
become  quite  dry,  one  finds  that  the 
longest  gills  which  have  separated  into 
two  halves  to  their  bases,  have  covered  in 
the  shorter  ones.  Each  fasciculus  of  gills  in  cross  section  now 
presents  a  very  curious  appearance  (Fig.  41,  F).  It  is  evident 
that  the  relative  sizes  and  amounts  of  splitting  of  the  different 
gills  are  admirably  adapted  to  facilitate  the  closing  up  of  the 
fasciculi.  In  a  state  of  desiccation  a  fruit-body  has  its  hymenium 
completely  hidden  from  external  view,  and  the  pileus  is  temporarily 
provided  below  with  a  hairy  covering. 

Whilst  in  the  dried  condition  a  fruit-body  can  retain  its 
vitality  for  at  least  two  years,  and,  with  intermittent  revivals, 
for  at  least  three  years.  When  rain  comes  again,  the  woolly 
upper  surface  of  the  pileus  sucks  water  in  by  capillary  attraction, 
and  the  gill  halves  at  once  begin  to  unroll  and  reappose  themselves 


FIG.  44.— Section  through  a 
fasciculus  of  gills  of  Sckizo- 
phyllum  commune  showing  an 
early  stage  in  the  divergence 
of  the  gill  plates.  About 
8  times  the  natural  size. 


n8 


RESEARCHES   ON   FUNGI 


in  pairs.  In  the  course  of  two  or  three  hours  the  gills  become 
perfectly  reconstructed,  and  they  are  then  directed  downwards 
in  the  normal  manner  (Fig.  41,  E,  and  Fig.  42).  The  hymenial 
layer  resumes  its  activity,  and,  after  three  or  four  hours  of  access 
to  moisture,  the  emission  of  spores  is  vigorously  recommenced. 

The  mechanism  involved  in  the  closing  and  opening  of  a 
pileus  can  be  partially  explained  from  anatomical  considerations. 
The  main  mass  of  each  gili  plate  consists  of  downwardly  running 


FlQ.  45. — Schizophyllum  commune.  Above,  a  transverse  section 
through  a  half-gill  taken  in  a  vertical  direction  ;  below,  another 
transverse  section  taken  in  a  horizontal  direction,  h,  the  hy- 
menium ;  s,  the  subhymenium  ;  t,  the  trama  ;  i,  the  inner  free 
hairy  surface  of  the  half-gill  which  becomes  exposed  on  desic- 
cation of  the  fruit-body.  Magnification,  688. 

tramal  hyphse,  which  have  very  thick  walls  and  are  strongly  attached 
together  at  intervals.  On  the  other  hand,  the  hymenium  and 
subhymenium  are  composed  of  elements  with  relatively  very  thin 
walls  (Figs.  45).  When  a  fruit-body  dries  up,  the  cell-walls  of  the 
hymenial  and  subhyrnenial  layers  contract  much  more  strongly 
in  the  vertical  direction  than  those  of  the  tramal  layer.  This 
being  so,  the  curling  up  of  each  gill  plate,  when  water  is  lost 
from  it,  is  a  mechanical  necessity.  When  a  gill  reabsorbs  moisture, 
the  walls  of  the  hymenial  and  subhyinenial  layers  expand  to  a 
greater  extent  than  those  of  the  trama.  The  tramal  hyphse  are 


SCHIZOPHYLLUM   COMMUNE  119 

thus  permitted  to  straighten  themselves  again.  The  straightening 
out  of  the  gill  plates,  however,  is  brought  about  by  something 
more  than  mere  cell-wall  imbibition  and  stretching.  This  is 
proved  by  the  fact  that  the  dry  gills  of  dead  fruit-bodies  are  not 
capable  of  becoming  entirely  uncurled.  Partial  recovery  of  the 
gills  was  observed :  (1)  In  fruit-bodies  which  had  lost  their  vitality 
when  kept  for  sixteen  years  in  the  dried  condition,  and  (2)  in  fresh 
fruit-bodies  which  were  dried  and  then  caused  to  absorb  a  solution 
of  1  per  cent,  corrosive  sublimate  through  their  upper  surfaces. 
The  first  and  major  part  of  the  straightening  out  of  the  gills  we 
may  regard  as  a  mechanical  process  connected  with  the  swelling 
of  cell-walls.  On  the  other  hand,  the  final  apposition  of  the  two 
plates  of  each  gill  appears  to  be  brought  about  by  the  resumption 
of  turgidity  by  the  hymenial  and  subhymenial  elements.  The  finer 
part  of  the  whole  readjustment,  according  to  this  interpretation,  is 
traceable  to  the  semipermeable  properties  of  living  protoplasm. 

The  division  of  the  gills  of  Schizophyllum  into  two  plates  is 
significant  in  that  it  permits  of  the  hymenial  surfaces  being  pro- 
tected during  periods  of  drought.  The  rapid  curling  up  of  the  gill 
plates  on  the  advent  of  dry  weather  must  serve  to  check  the  rate 
of  loss  of  water  from  the  fruit-body  by  limiting  the  amount  of 
gill  surface  exposed  to  the  outer  air.  This  closing  oft'  of  most  of 
the  transpiring  gills  at  the  beginning  of  desiccation,  finds  its  analogy 
in  the  curling  up  of  the  leaves  of  many  xerophytic  Phanerogams 
under  similar  atmospheric  conditions.  However,  I  am  not  inclined 
to  think  that  reduction  in  the  rate  of  transpiration  is  the  chief 
advantage  gained  by  the  opening  out  of  the  gill  plates.  Periods  of 
drought  are  often  very  long,  and  when  they  occur  it  may  be  of 
considerable  advantage  for  a  fruit-body  to  have  its  delicate  hymenial 
surfaces,  covered  as  they  are  with  millions  of  spores,  made  as  inac- 
cessible as  possible  to  various  small  marauding  animals.  However, 
the  exact  ecological  significance  of  the  opening  out  of  the  gill 
plates  would  best  be  elucidated  in  the  tropics,  where  the  genus 
Schizophyllum  is  richest  in  species. 


CHAPTER    X 

EXTERNAL  CONDITIONS  AND  SPORE-DISCHARGE— THE  EFFECTS 
OF  LIGHT,  GRAVITY,  HYGROSCOPIC  CONDITION  OF  THE  AIR, 
HEAT,  ALTERATION  IN  THE  GASEOUS  ENVIRONMENT,  AND 
OF  ANAESTHETICS 

LIKE  all  other  active  processes  of  living  organisms,  the  discharge  of 
spores  can  only  be  carried  on  when  external  conditions  are  favour- 
able. It  is  now  necessary  to  consider  these  conditions  in  detail. 

The  Effect  of  Light. — Whilst  in  some  species,  e.g.  the  Mush- 
room, the  fruit-bodies  can  undergo  perfect  development  in  total 
darkness,  in  a  number  of  others  the  pilei  cannot  be  produced 
without  a  morphogenic  stimulus  given  by  light.  Among  the  latter 
are  Lentinus  lepideus  and  Polyporus  squamosus.  When  a  fruit- 
body  of  either  of  these  species  is  grown  entirely  in  the  dark,  it 
develops  into  a  horn-like  process  without  the  least  trace  of  a  pileus 
or  hymenium  (Fig.  16,  D,  p.  48,  and  Fig.  20,  p.  58).  It  was  found  for 
Polyporus  squamosus,  however,  that,  when  the  development  of  the 
pileus  has  once  been  initiated  in  response  to  the  stimulus  of  light, 
if  the  fruit-body  is  then  placed  in  the  dark,  further  development 
continues  in  a  normal  manner :  the  usual  hymenial  tubes  are 
produced  and  the  hymenium  gives  rise  to  ordinary  basidia  which 
liberate  spores  in  continuous  clouds.  The  production  of  spores  in 
clouds  in  the  dark,  which  in  one  instance  lasted  for  eleven  days, 
proves  conclusively  that,  for  Polyporus  squamosus  at  least,  the 
liberation  of  spores  is  quite  independent  of  light  conditions.  For 
species  of  Polystictus,  Lenzites,  Schizophyllum,  &c.,  spore-discharge 
was  found  to  be  quite  continuous.  The  alternation  of  night  and 
day  appeared,  as  judged  by  the  beam-of-light  method,  to  make  no 
difference  whatever  to  the  rate  at  which  spores  left  the  fruit-bodies. 
It  is  probably  correct  to  state  quite  generally  for  the  Hymeno- 
mycetes  that,  whilst  the  morphogenic  stimulus  of  light  may  or  may 


EXTERNAL  CONDITIONS  AND  SPORE-DISCHARGE     121 

not  be  necessary  for  the  production  of  the  hymeniurn,  when  once 
the  hymenium  has  begun  its  development,  the  basidia  discharge 
their  spores  quite  independently  of  light  conditions. 

In  the  case  of  certain  Ascomycetes,  e.g.  Ascobolus,  it  has 
long  been  observed  that  spore-discharge  is  periodic,  a  certain 
number  of  asci  ejecting  their  spores  each  day.  This  phenomenon 
has  come  more  particularly  under  my  notice  in  the  case  of 
Ascobolus  immersus  growing  on  horse  dung.  The  periodicity 
depends  on  the  alternation  of  day  and  night,  and  can  be  given 
an  easy  ecological  explanation.  It  is  important  for  the  purpose 
of  distribution  that  the  ejected  spores  should  be  thrown  clear  of 
obstacles,  e.g.  dung  balls,  &c.  The  asci  are  positively  heliotropic, 
and  during  the  day  always  turn  themselves  in  response  to  the 
stimulus  of  light,  so  that  they  point  toward  open  spaces.  Such 
an  adjustment  would  be  impossible  at  night.  The  periodic 
discharge  of  asci  each  day  is  therefore  of  advantage  in  that  it 
ensures  that  these  structures  shall  burst  only  after  the  light  has 
caused  them  to  take  up  the  most  favourable  positions  for  spore- 
dissemination.  On  the  other  hand,  as  my  observations  have  made 
clear,  spore-discharge  in  the  Hymenomycetes  is  continuous  and 
does  not  take  place  at  intermittent  periods.  The  general  arrange- 
ment of  a  Mushroom  or  Polyporus  is  such  that,  under  normal 
conditions,  the  basidia  never  face  obstacles.  All  that  is  required 
for  the  successful  liberation  of  the  spores  is  that  the  basidia  shall 
shoot  them  straight  outwards  from  the  hymenium  for  a  minute 
distance.  After  being  violently  expelled  from  their  sterigmata, 
the  spores  drop  into  the  spaces  between  the  gills,  in  the  hymenial 
tubes,  &c.,  and  thus  fall  from  the  fruit-body  and  are  carried  off* 
by  air-currents  without  coming  into  contact  with  any  impediment.1 
Almost  without  exception  in  the  Hymenomycetes,  the  orientation 
of  the  hymenium,  and  with  it  the  direction  of  spore-discharge, 
is  finally  determined  by  the  stimulus  of  gravity,  and  is  of  such 
a  nature  as  to  ensure  that  the  spores  shall  fall  out  of  the  fruit- 
body.  The  perfect  indifference  to  light  as  regards  spore-discharge 
by  the  fruit-bodies  of  Hymenomycetes  in  comparison  with  certain 
Ascomycetes  is  thus  elucidated. 

1  Vide  infra,  Chap.  XVII. 


122  RESEARCHES   ON  FUNGI 

The  Effect  of  Gravity. — Gravity  is  the  chief  orienting  stimulus 
acting  on  the  fruit  -  bodies  of  Hymenoruycetes.  In  Polyporus 
squamosus,  for  instance,  as  we  have  already  seen  from  the  dis- 
cussion in  Chapter  IV.,  it  causes  :  (1)  The  stipe  to  turn  the 
rudimentary  and  terminal  pileus  into  a  horizontal  position,  (2)  the 
pileus  to  grow  with  a  symmetry  suited  to  the  position  of  the 
stipe,  (3)  the  pileus  flesh  to  grow  parallel  to  the  earth's  surface, 
and  (4)  the  hymenial  tubes  to  grow  towards  the  earth's  centre. 
The  stiped  Agaricinese  usually  have  stipes  which  are  negatively 
geotropic  and  gills  which  are  positively  geotropic. 

Although  the  stimulus  of  gravity  is  of  the  greatest  importance 
in  orienting  the  hymenium  and  the  basidia  which  it  contains, 
it  appears  to  have  no  direct  effect  on  the  process  of  spore-dis- 
charge. When  a  hymenium  has  once  started  its  development, 
ripe  spores  continue  to  be  developed  and  separated  from  the 
basidia,  independently  of  the  direction  of  gravitational  attraction. 
Thus,  if  a  gill  be  placed  so  that  the  basidia  on  one  side  look 
upward  or  downwards  or  at  any  angle  with  the  vertical  what- 
soever, spore  -  discharge  takes  place  equally  well  in  all  cases. 
Evidence  of  this  was  obtained  by  watching  spores  leave  their 
sterigmata  with  the  microscope,  and  will  be  given  in  the  next 
chapter,  which  deals  with  the  violent  projection  of  spores  from 
the  hymenium. 

The  Effect  of  the  Hygroscopic  Condition  of  the  Air.— It  has 
been  mentioned  already  *  that  for  Polyporus  squamosus,  so  far  as 
it  was  possible  to  judge  from  the  spore-clouds  seen  by  daylight, 
the  liberation  of  spores  takes  place  equally  well  both  in  a  dry 
and  in  a  saturated  atmosphere.  For  this  species,  therefore, 
ordinary  variations  in  the  hygroscopic  state  of  the  atmosphere 
do  not  appear  to  appreciably  affect  the  rate  of  discharge  of  the 
spores. 

When  a  small  portion  of  a  pileus  of  Polyporus  squamosus, 
PsaUiota  campestris,  or  Amanitopsis  vaginata,  &c.,  was  placed  in 
a  vertically  disposed  compressor  cell  (cf.  Fig.  58,  p.  167,  and  Plate  IV., 
Fig.  29),  so  that  the  fall  of  spores  could  be  watched  with  a  hori- 
zontal microscope,  it  was  found  that  spores  fell  continuously  when 
1  Chap.  VI. 


EXTERNAL  CONDITIONS  AND  SPORE-DISCHARGE     123 

the  chamber  was  saturated  with  moisture.  When  crystals  of 
calcium  chloride  were  placed  in  the  cell,  the  spores  continued 
to  fall  for  some  time,  until  the  piece  of  pileus  had  shrunk 
appreciably  and  was  evidently  drying  up. 

It  can  easily  be  observed  with  the  beam-of-light  method  that, 
if  a  fruit -body  of  Polystictus  versicolor,  Lenzites  betulina,  &c., 
is  allowed  to  dry  up  slowly,  when  a  certain  amount  of  water  has 
been  lost,  the  rate  of  spore-discharge  becomes  slower  and  slower. 
As  desiccation  proceeds  spore-fall  ceases  altogether.  Insufficient 
access  to  water  must  often,  in  nature  as  in  the  laboratory, 
especially  in  the  case  of  the  xerophytic  fruit-bodies  growing  on 
logs  ,and  sticks,  lessen  the  rate  of  spore-discharge  and  lead  to  a 
corresponding  increase  in  'the  length  of  the  spore-fall  period. 

The  general  conclusion,  to  which  numerous  observations  of 
the  kind  just  described  have  led  me,  is  that,  so  long  as  a  fruit- 
body  has  sufficient  moisture  in  itself,  the  dryness  or  dampness 
of  the  atmosphere  without  makes  no  appreciable  difference  to 
the  rate  of  spore-discharge. 

The  Effect  of  Heat. — The  liberation  of  spores,  like  all  other 
vital  processes,  can  only  be  carried  on  within  certain  limits  of 
temperature.  Doubtless  each  species  has  its  own  particular 
minimum,  optimum,  and  maximum  for  this  function. 

In  all  the  species  so  far  investigated,  the  discharge  of  spores 
takes  place  rapidly  at  ordinary  room  temperatures.  It  slackens, 
however,  when  the  temperature  is  sufficiently  lowered  ;  but  in 
several  instances  it  was  found  to  continue  even  at  the  freezing 
point  of  water,  although  with  much  diminished  vigour.  A  slowing 
down  of  the  rate  of  spore-discharge  also  occurs  when  the  tem- 
perature is  gradually  raised  above  the  normal;  and  when  a 
certain  temperature  has  been  reached,  the  hymenium  becomes 
altogether  inactive.  The  maximum  temperature  for  the  discharge 
of  spores,  however,  is  appreciably  lower  than  the  maximum  for 
vitality. 

For  the  purpose  of  determining  whether  spore-fall  still  continues 
at  freezing  point,  a  cold- room  was  made  use  of.  The  room  had 
two  doors,  one  opening  out-of-doors  and  the  other  into  a  passage 
within  the  University  building.  The  temperature  of  the  room 


124 


RESEARCHES   ON  FUNGI 


remained  for  hours,  and  sometimes  for  days,  between  0°  and  3°  C. 
By  opening  the  outer  door  for  a  few  minutes  the  air  of  the  room 
could  easily  be  reduced  to  0°  C.,  and  this  temperature  was  often 
maintained  for  several  hours. 

So  far  experiments  have  been  limited  to  species  which  grow 
upon  wood  and  have  proved  capable  of  withstanding  uninjured 
the  prolonged  and  severe  frost  of  the  Manitoban  winter.  Dried 
fruit- bodies  of  Lenzites  betulina,  Polystictus  versicolor,  P.  hirsutus, 
Diedalea  unicolor,  and  Schizophyllum  commune  were  placed  in 
a  damp-chamber  with  wet  cotton-wool  upon  the  upper  surfaces 

of  their  pilei. 
They  soon  re- 
vived, and  at  the 
end  of  six  hours, 
upon  being  ex- 
amined with  a 
beam  of  light, 
they  were  found 
to  be  vigorously 
shedding  spores. 
A  fruit-body,  to 

FlG.  46. — Apparatus  for  demonstrating  the  fall  of   spores  from  u~     f^ci-prl  wa<s 

fruit-bodies  at  0°  C.     A  glass  dish  u  is  placed  on  a  wooden  D  eU>  1 

shelf  w  in  the  cold-room.     An  inverted  glass  dish  i  is  packed  taken      to  the 
round  with  snow  s  so  as  to  leave  the  space  within  it  unfilled.        . 

To  the  cork  c  is  attached  the  fruit-body/,  below  which  is  COld-room  and 
placed  a  glass  slide  g  for  the  purpose  of  catching  the  falling                 T  .  i 

spores.     About  J  actual  size.  pinned  to  a  Cork 

attached      by 

means  of  sealing-wax  to  the  bottom  of  a  small  crystallising  dish.  This 
was  then  inverted  and  packed  round  with  melting  snow  contained 
in  another  and  much  larger  crystallising  dish,  as  shown  in  Fig.  46. 
After  two  hours,  when  the  fruit-body  had  become  cooled  to  freezing 
point,  the  cold-room  air  was  reduced  to  0°  C.  by  opening  the  outer 
door  for  a  few  minutes.  The  inverted  crystallising  dish,  to  which 
the  fruit-body  was  attached,  was  then  lifted  out  of  the  snow,  so 
that  fresh  spore-free  air  at  0°  C.  entered  it.  A  glass  slide  (Fig.  46,  g) 
was  then  placed  so  that  when  the  crystallising  dish  was  replaced 
in  position,  the  fruit-body  had  its  natural  orientation,  its  under, 
spore-producing  surface  looking  directly  down  on  the  glass  slide. 


EXTERNAL  CONDITIONS  AND  SPORE-DISCHARGE     125 

After  two  hours  the  slide  was  removed  and  examined  under  the 
microscope.  Any  spores  which  had  fallen  upon  it  could  be  detected 
with  ease. 

The  results,  obtained  from  a  number  of  experiments  of  the 
kind  just  described,  have  served  to  convince  me  that  Dssdalea 
unicolor,  Lenzites  betulina,  Poly st  ictus  versicolor,  and  P.  hirsutus 
continue  to  shed  their  spores  at  the  freezing  point  of  water. 
However,  the  comparatively  small  number  of  spores  which  settled 
upon  the  glass  slides  each  hour  showed  that  spore-discharge  is 
not  nearly  so  active  at  0°  C.  as  at  higher  temperatures.  From  a 
succession  of  tests  it  was  found  that  Lenzites  betulina  continued 
to  shed  its  spores  at  0°  C.  for  at  least  three  days.  A  fruit-body 
of  this  species,  whilst  enclosed  in  the  snow-chamber,  set  free 
sufficient  spores  in  a  few  hours  to  make  a  distinct,  although  faint, 
macroscopic  pattern  of  the  gills  upon  a  glass  slide.  Probably, 
in  all  species  which  shed  spores  at  0°  C.,  the  discharge  of  spores 
continues  for  an  indefinite  period  of  time  until  the  fruit-bodies 
become  exhausted.  No  spore-deposit  was  detected  as  being  pro- 
duced by  Schizophyllum  commune  at  0°  C.,  although  spores  were 
vigorously  shed  by  this  species  at  5°  C. 

Ontogenetic  study  shows  that  the  basidia  of  a  hymenium  come 
to  maturity  successively,  and  part  with  their  spores  as  soon  as 
these  are  ripe.  The  shedding  of  spores  by  Lenzites  betulina, 
Dasdalea  unicolor,  &c.,  in  a  snow-chamber  indicates  that  in  these 
fungi  the  development  of  the  hymenium  can  still  continue  at 
the  freezing  point  of  water.  At  first,  the  fact  that  growth  is 
still  possible  in  a  hymenomycetous  fruit-body  at  0°  C.,  may  seem 
surprising,  but  parallel  instances  of  growth  at  this  and  even  lower 
temperatures  in  other  plants  are  by  no  means  unknown.  Thus 
in  Pfeffer's1  list  of  cardinal  points  for  growth,  the  minima  for 
Sinapis  alba  (Kirchner  and  de  Vries),  Ulothrix  zonata  (Klebs), 
and  Bacillus  cyano-fuscus  (Beyerinck)  are  given  as  0°  C.,  and  on 
Arctic  coasts,  according  to  Kjellman,2  algse  flourish  in  sea-water 
whose  temperature  falls  to  —1-8  and  perhaps  never  exceeds  0°  C. 
The  fruit-bodies  of  species  of  Stereum,  Corticium,  &c.,  often  appear 

1  Pfeffer,  Physiology  of  Plants,  translated  by  A.  J.  Ewart,  vol.  ii.,  1903,  p.  77. 

2  Kjellman,  Bot.  ZeiL,  1875,  p.  171. 


126  RESEARCHES   ON  FUNGI 

to  be  at  their  best  in  the  middle  of  an  English  winter,  from 
which  fact  it  seems  justifiable  to  conclude  that  cold  weather  is 
favourable  to  their  development. 

The  effect  of  high  temperatures  upon  spore-discharge  has  been 
investigated  only  in  the  case  of  Lenzites  betulina.  The  fruit-body 
to  be  tested  was  first  determined  to  be  freely  shedding  spores  by  the 
beam-of-light  method.  It  was  then  pinned  to  a  cork  fixed  to  a  glass 
plate,  after  which  the  plate  was  placed  over  a  beaker,  so  that  the 
fruit-body  assumed  its  normal  orientation  (cf.  Fig.  37,  p.  97).  This 
beaker  with  its  cover,  and  another  similar  but  uncovered  beaker,  were 
then  placed  in  the  incubator,  the  air  of  which  had  been  raised  to  the 
desired  temperature.  After  from  thirty  minutes  to  two  hours,  when 
doubtless  the  fruit-body  had  assumed  the  temperature  of  the  incu- 
bator, the  plate  was  quickly  taken  from  the  first  beaker  and  set  upon 
the  second.  The  air  within  the  second  beaker  before  this  operation 
was,  of  course,  free  from  spores,  whereas  that  of  the  first  might  still 
have  contained  spores  which  had  been  liberated  by  the  fruit-body 
before  this  had  become  heated.  After  another  fifteen  or  thirty 
minutes,  the  second  beaker  was  removed  from  the  incubator  and 
immediately  examined  by  the  beam-of-light  method.  If  spores  had 
been  liberated  into  it,  they  could  easily  be  seen  floating  in  the  air. 

As  a  result  of  experiments  of  the  kind  just  described,  it  was 
found  that  the  discharge  of  spores  took  place  slowly  at  29°  C.,  but 
not  at  33°,  43°,  or  46°.  The  fruit-bodies,  however,  were  not  killed  by 
exposure  for  forty-five  minutes  to  these  high  temperatures,  for  when 
they  were  afterwards  placed  in  a  moderately  heated  room,  in  the 
course  of  several  hours  they  recovered  and  shed  spores  again  in 
abundance. 

The  modes  of  action  of  extreme  cold  and  of  extreme  heat  are 
doubtless  different.  Extreme  cold  must  slow  down  the  metabolism 
and  hence  prevent  spore  development.  No  injury  in  the  case  of 
Lenzites,  Dsedalea,  and  other  similar  fruit-bodies  growing  on  logs, 
results  from  a  long  exposure  to  very  low  temperature,  e.g.  from  —15° 
to  —  40°  C.,  such  as  occur  often  for  weeks  together  in  the  course  of 
winter  at  Winnipeg.  As  soon  as  a  fruit-body  is  warmed  sufficiently, 
spore-fall  begins  anew.  Fruit-bodies  of  Lenzites  betulina,  Stereumpur- 
pureum,  and  Schizophyllum  commune  were  gathered  from  a  wood- 


EXTERNAL  CONDITIONS  AND  SPORE-DISCHARGE     127 

pile  in  March  at  about  — 17°  C.  after  being  exposed  for  several  months 
to  severe  frost.  When  brought  into  the  laboratory  they  soon  began 
to  shed  their  spores,  and  within  a  few  hours  produced  well-marked 
spore-deposits.1  On  the  other  hand,  extreme  heat  probably  causes 
a  heat  rigor,  for  when  some  fruit-bodies  of  Lenzites  betulina  were 
exposed  to  a  temperature  of  39°  C.  for  half-an-hour  and  then  cooled 
to  an  ordinary  room  temperature,  two  hours  passed  by  before  the 
fall  of  spores  was  resumed. 

The  range  of  temperature  which  permits  of  spore-discharge — for 
Lenzites  betulina  about  0°  to  30°  C. — probably  coincides  with  the 
range  of  temperature  permitting  the  growth  and  development  of  the 
spores.  As  soon  as  the  spores  are  ripe  they  are  probably  shot  off. 
If  one  watches  the  discharge  of  spores  from  the  basidia  with  the 
microscope,  one  finds  that  spores  which  look  ripe,  i.e.  which  have 
attained  their  full  size  and  proper  colour,  do  not  long  remain  on 
their  sterigmata.  The  rate  of  spore-discharge  seems,  therefore,  to  be 
an  indication  of  the  rate  of  spore  development. 

So  far,  opportunity  has  not  been  found  for  determining  the  range 
of  temperature  within  the  limits  of  which  the  liberation  of  spores  is 
possible  for  succulent,  non-xerophytic,  ground  Agarics  which  flourish 
during  summer.  It  seems  to  me  probable,  however,  that  for  many 
species,  e.g.  the  Mushroom,  the  minimum  temperature  for  shedding 
spores  is  several  degrees  above  the  freezing  point  of  water.  To  what 
extent  frost  is  fatal  to  the  reproductive  organs  of  Hymenomycetes 
still  requires  investigation. 

The  Effect  of  Alteration  in  the  Gaseous  Environment. — The 
pileus  of  a  small  fruit-body  of  Marasmius  oreades,  about  1  inch  in 
diameter,  was  divided  into  three  portions.  One  of  them  was  placed 
in  a  suitable  glass  vessel  of  about  O75  litres  capacity,  through 
which  a  strong  stream  of  hydrogen  was  made  to  flow  for  ten  minutes. 
The  stop-cocks  were  then  closed.  By  similar  means  the  second 
portion  of  the  pileus  was  surrounded  by  an  atmosphere  of  carbon 

1  Possibly  the  fruit-bodies  began  to  shed  their  spores  immediately  they  had 
been  unthawed  and  raised  to  the  temperature  of  the  laboratory.  Unfortunately, 
when  these  experiments  were  made,  I  had  not  developed  the  beam-of-light 
method,  and  the  formation  of  a  macroscopic  spore-deposit  was  relied  upon  as  a 
test  for  the  liberation  of  spores. 


128  RESEARCHES   ON  FUNGI 

dioxide,  whilst  the  third  was  set  in  a  chamber  containing  ordi- 
nary air.  Glass  slides  were  employed  to  catch  any  spores  which 
might  fall. 

The  piece  of  pileus  in  air  shed  abundance  of  spores,  a  good  deposit 
outlining  the  gills  being  collected  in  the  short  space  of  ten  minutes. 
A  thick  deposit  had  formed  in  an  hour,  and  in  the  course  of  twenty 
hours  tens  of  thousands  of  spores  had  collected.  The  piece  of  pileus 
placed  in  hydrogen  shed  a  few  spores  during  the  first  hour.  At  the 
end  of  this  time  it  was  removed  to  a  new  position  on  the  glass  slide. 
During  the  subsequent  nineteen  hours  scarcely  a  spore  fell.  The 
few  spores  found  on  the  slide  with  the  microscope  certainly  did  not 
make  up  one  five-hundredth  part  of  the  number  which  fell  from  the 
piece  of  pileus  placed  in  air.  A  similar  result  was  obtained  with 
the  piece  of  pileus  placed  in  carbon  dioxide.  During  the  first 
hour  in  that  gas  a  few  spores  were  liberated.  The  piece  of  pileus 
was  then  pushed  to  a  new  position  on  the  glass  slide.  During 
the  subsequent  nineteen  hours  practically  no  further  spores  became 


The  conclusion  to  which  the  experiments  just  described  appear 
to  point  is  that,  in  the  absence  of  oxygen,  spore-discharge  soon 
ceases.  Doubtless  for  some  time  after  a  piece  of  pileus  has  been 
placed  in  hydrogen  or  carbon  dioxide,  the  basidia  have  access  to 
a  certain  amount  of  oxygen  diffusing  outwards  from  the  pileus 
through  the  hymenium.  Possibly  it  is  on  this  account  that  a  few 
spores  still  continue  to  be  liberated  for  a  short  time  after  the 
oxygen  has  been  removed  from  the  surrounding  atmosphere.  We 
may  conclude  by  analogy  that  the  direct  action  of  hydrogen  on  the 
pileus  is  harmless,  but  that  that  of  carbon  dioxide  may  possibly  be 
poisonous. 

Removal  of  oxygen  from  the  atmosphere  probably  causes  cessa- 
tion of  growth  of  the  basidia.  With  this  cessation  of  growth 
the  fall  of  spores  must  cease,  for  the  continuous  raining  down 
of  spores  from  the  gills  depends  on  the  successive  development  of 
the  basidia. 

Two  small  pilei,  one  of  Marasmius  oreades  and  the  other  of 
Psilocybe  fcenisecii,  were  halved.  One  piece  of  each  was  covered  by 
a  glass  vessel  containing  air,  and  the  other  pieces  were  placed  in  a 


EXTERNAL  CONDITIONS  AND  SPORE-DISCHARGE     129 

chamber  of  0*75  litres  capacity,  through  which  a  strong  stream  of 
oxygen  was  made  to  flow  for  some  minutes.  The  stop-cocks  were 
then  closed.  The  pieces  of  pileus  were  set  on  glass  slides  so  that  any 
falling  spores  might  be  caught. 

After  an  hour,  apparently  equally  thick  deposits  of  spores  had 
been  shed  both  in  air  and  in  the  pure  oxygen.  The  half-pilei  were 
then  placed  in  new  positions  on  the  glass  slides.  During  this  opera- 
tion air  was  kept  out  of  the  oxygen  chamber  by  means  of  a  strong 
stream  of  oxygen  passed  through  it.  Five  hours  subsequently  the 
new  spore-deposits  were  examined.  They  appeared  to  be  equally 
thick  in  both  air  and  pure  oxygen.  The  half-pilei  were  again 
placed  in  new  positions  on  the  glass  slides.  These  were  once  more 
examined  after  an  interval  of  eighteen  hours.  Heavy  spore-deposits 
resembling  each  other  had  again  formed  both  in  the  air  and  in  the 
oxygen. 

This  experiment  seems  to  prove  that,  in  an  atmosphere  of  pure 
oxygen,  the  fruit-bodies  of  the  two  species  examined  continue  to 
develop  their  basidia  and  to  shed  their  spores  in  the  usual  manner. 
This  need  not  occasion  surprise,  for  many  even  of  the  higher  plants 
develop  normally  in  pure  oxygen  or  under  a  pressure  of  five 
atmospheres  of  air.1 

The  Effect  of  Anaesthetics.— An  observation  with  an  anaesthetic 
has  already  been  made  by  Falck.  He  found  that  a  fruit-body  of 
Agaricus  nebularis,  on  being  subjected  to  chloroform  vapour, 
ceased  to  shed  spores,  and  he  drew  the  conclusion  from  this  fact 
that  spore-liberation  is  an  active  process.2  Experiments  with 
anaesthetics,  however,  do  not  decide  whether  the  spores  are  set 
free  by  a  process  of  growth  and  thus  simply  fall  when  ripe  like 
apples,  or  whether,  on  the  contrary,  they  are  shot  outwards  from 
their  sterigmata  with  force.  In  the  next  chapter  this  matter  will 
be  dealt  with  in  detail. 

In  order  to  test  the  effect  of  ether  vapour  upon  the  liberation 
of  spores,  the  following  method  was  resorted  to.  A  piece  of  cork 
was  fixed  by  means  of  sealing-wax  to  the  middle  of  a  circular 

1  Pfeffer,  Physiology  of  Plants,  vol.  i.  p.  540. 

2  R.  Falck,  "Die  Sporenverbreitung  bei  den  Basidiomyceten/'  Beitrage  zur 
Biologic  der  Pflanzen,  Bd.  IX.,  1904,  p.  27,  footnote. 

I 


130  RESEARCHES   ON  FUNGI 

plate  of  glass,  and  to  it  a  fruit-body  to  be  tested  was  pinned. 
The  glass  plate  was  then  placed  on  the  ground  top  of  a  cylindrical 
glass  jar  of  1-25  litres  capacity,  so  that  the  fruit-body  had  its 
natural  orientation  (cf.  Fig.  37,  p.  97).  A  piece  of  blotting-paper 
was  attached  with  sealing-wax  to  the  bottom  of  the  jar. 

The  fruit-body  was  first  tested  in  the  usual  way  with  a  beam 
of  light  to  find  out  whether  spore-discharge  was  taking  place. 
In  all  cases  a  cloud  of  spores  could  easily  be  seen  coming  from 
the  lower  surface.  When  it  had  thus  been  determined  that 
spores  were  being  freely  liberated,  the  glass  cover,  with  the  fruit- 
body  attached,  was  removed,  inverted,  and  placed  on  a  table. 
Fresh  spore-free  air  was  caused  to  enter  the  now  open  jar.  By 
means  of  a  pipette  O5  cc.  of  Squibb's  ether  was  then  quickly 
dropped  on  to  the  blotting-paper  in  the  jar  and  the  latter 
immediately  inverted  over  the  glass  cover,  to  which  it  became 
closely  attached  by  means  of  vaseline.  When  a  fruit-body  is 
upside  down  it  is  unable  to  liberate  any  of  its  spores  into  the 
air  in  a  glass  chamber.  So  long,  therefore,  as  the  fruit-body 
was  kept  inverted,  the  air  in  the  jar  above  it  remained  spore-free. 
When  it  was  desired  to  find  out  whether  spores  could  still  be 
liberated,  the  anaesthetised  fruit-body  was  turned  into  the  normal 
position  again  by  means  of  another  inversion  of  the  jar.  The  air 
beneath  the  now  downwardly-looking  hymenium  was  then  examined 
for  spore  contents  with  a  beam  of  light.  It  was  found  that,  when 
the  jar  was  placed  upright  again  two  minutes  after  its  first 
inversion,  no  spores  fell  into  the  air  within.  The  ether  vapour, 
therefore,  caused  cessation  of  spore-discharge  in  two  minutes. 

When  the  ether  was  added  to  an  upright  jar,  and  the  cover, 
bearing  a  normally  oriented  fruit-body,  was  placed  on  the  top, 
at  first  the  spore  clouds  could  easily  be  seen  coming  off  from  the 
underside  of  the  fruit-body  with  the  beam  of  light ;  but  the 
spore  stream  quickly  diminished  in  density  and  its  emission 
ceased  after  about  two  minutes.  The  spores  which  had  already 
entered  the  jar  then  spread  themselves  evenly  in  the  air  which 
it  contained. 

When  the  jar  in  the  first  described  experiments  was  placed  in 
the  upright  position  a  few  minutes  after  the  ether  had  been 


EXTERNAL  CONDITIONS  AND  SPORE-DISCHARGE     131 

added,  the  fruit-body  was  always  found  to  have  lost  its  power  of 
shedding  spores.  Not  a  single  spore  could  be  seen  floating  in  the 
beam  of  light,  nor,  so  long  as  the  fruit-body  remained  subjected 
to  the  anaesthetic,  were  any  spores  liberated.  When,  however,  the 
fungus  was  removed  from  the  glass  jar  and  exposed  to  ordinary 
air,  it  gradually  recovered.  It  was  found  that,  even  after  treat- 
ment with  ether  vapour  for  a  week,  recovery  could  still  take  place 
and  active  spore-discharge  be  resumed.  The  length  of  time  during 
which  fruit-bodies  were  exposed  to  ether  vapour,  and  the  length  of 
time  required  for  recovery  of  the  spore-liberating  function  after 
removal  from  the  anaesthetic,  are  given  in  the  following  table: — 

Lenzites  betulina. 
0-5  cc.  Squibb's  ether  in  a  1'25  litre  jar. 

Time  taken  for  Recovery  of  the  Spore- 
Length  of  Exposure  to  the  liberatinsr  Function  after  Removal 
Ether  Vapour.  from  Ether  Vapour. 

5  minutes         ....     Less  than  30  minutes. 
30  minutes         ....     More  than  2  hours. 
12  hours    .....     About  3  hours. 

,  j  More  than  3  hours  45  minutes. 

I  Less  than  4  hours  35  minutes. 
7  days      .         .         .         .         .6  hours  30  minutes. 

It  is  clear  that  the  longer  the  fruit-bodies  were  exposed  to 
the  anaesthetic,  the  longer  was  the  time  required  to  recover  from 
the  effects. 

The  chief  result  of  these  experiments  is  to  show  that  spore- 
discharge  may  be  inhibited  by  ether  without  any  apparent 
permanent  injury  to  the  fruit-body.  The  shooting  off  of  the 
spores,  and  probably  their  development,  ceases  under  the  in- 
fluence of  ether  just  as  does  protoplasmic  movement  in  the  cells 
of  higher  plants  and  the  reactions  to  mechanical  stimuli  in  the 
leaves  of  Mimosa  pudica,  the  stamens  of  Berber  is,  &c.  As  in 
these  cases,  the  active  process  is  resumed  again  when  normal 
conditions  are  allowed  to  supervene. 

Chloroform  has  a  similar  effect  to  ether.  0*5  cc.  of  chloroform 
was  introduced  into  the  1-25  litre  jar  in  the  manner  already 
described.  Under  these  conditions  the  liberation  of  spores  ceased 
in  about  one  minute.  The  fruit- body  was  exposed  to  the  chloro- 


132  RESEARCHES   ON   FUNGI 

form  vapour  for  five  minutes  and  then  placed  in  ordinary  air. 
Recovery  of  the  spore-liberating  function  took  place  after  about 
fifteen  minutes.  It  might  be  expected  from  analogy  that  chloro- 
form would  prove  more  poisonous  to  the  fruit-bodies  than  ether. 
No  attempt,  however,  has  been  made  to  obtain  an  experimental 
basis  for  this  assumption. 


CHAPTER   XI 

THE  VIOLENT  PROJECTION  OF  SPORES  FROM  THE  HYMENIUM— 
METHODS  I.,  II.,  III.,  IV.,  AND  V.. 

IN  order  to  understand  the  arrangements  for  liberating  the  spores 
from  the  fruit-bodies  of  Hymenomycetes,  it  is  of  great  importancelto 
bear  in  mind  that  the  spores  are  very  adhesive.  After  they  have 
settled  on  paper,  glass,  ja  pileus,  or  stipe,  the  most  violent  shaking 
will  not  separate  them  from  the  surface  to  which  they  have  become 
attached.  They  cling  to  each  other  with  great  tenacity,  for  from 
spore-deposits  one  may  scrape  up  spore  ribbons  several  millimetres 
long.  If  a  ripe  Mushroom  or  other  fruit-body  be  turned  upside 
down  so  that  the  spores  after  leaving  the  sterigmata  settle  upon  the 
basidia  and  paraphyses  of  the  hymenium,  when  the  fruit-body  is 
again  placed  in  the  natural  position  not  one  of  the  fallen  spores 
succeeds  in  freeing  itself.  One  can  see  with  the  microscope  that  the 
spores  remain  fixed  where  they  fell.  When  a  fruit-body  is  inverted 
for  an  hour,  some  millions  of  spores  leave  the  sterigmata  and  settle 
on  the  gills.  If  the  spores  were  not  adhesive,  on  replacing  the  fruit- 
body  in  its  natural  position  and  observing  with  the  beam-of-light 
method,  one  should  be  able  to  see  these  millions  of  spores  falling  in 
the  form  of  a  dense  and  very  temporary  cloud.  No  such  cloud, 
however,  can  be  detected.  These  and  other  observations  of  various 
kinds  have  convinced  me  that,  if  a  spore  after  leaving  its  sterigmata 
happens  to  touch  the  hymenium  in  its  fall,  even  when  it  strikes  it 
very  obliquely,  it  immediately  gets  stuck  there,  and  never  succeeds 
in  reaching  the  outer  air. 

In  discussing  the  general  structure  of  the  fruit-bodies  it  was 
pointed  out  that  in  many  cases  the  hymenium  is  disposed  for  the 
most  part  in  almost  vertical  planes.  In  the  Agaricinese  it  is  situated 
on  the  surfaces  of  very  acutely  wedge-shaped  gills,  and  in  the 
Polyporese  it  lines  the  surfaces  of  very  slightly  conical  tubes.  In 


134  RESEARCHES   ON   FUNGI 

many  fruit-bodies  of  Agaricinese  the  declination  of  the  gill  surfaces 
from  the  vertical  is  only  from  one  to  three  degrees. 

Whilst  reflecting  on  the  adhesiveness  of  the  spores  and  the  ver- 
tical position  of  the  hymenial  surfaces,  I  asked  myself  the  question  : 
By  what  means  are  the  spores  enabled  to  fall  from  the  basidia  without 
contact  with  one  another,  and  in  such  a  manner  that  they  find  their 
way  down  hymenial  tubes  or  between  gills  without  becoming  attached 
to  the  sides  ?  Taking  into  consideration  that  the  horizontal  basidia 
are  crowded  one  above  the  other  (cf.  Fig.  56,  p.  165,  and  Plate  I., 
Fig.  3),  it  was  argued  that  if  the  adhesive  spores  merely  fell  from 
the  sterigmata  in  a  passive  manner,  they  would  very  frequently  fall 
upon  one  another,  and  that  of  necessity  they  would  fall  rather 
inwards  toward  the  hymenial  surface  than  outwards,  owing  to  the 
tendency  they  would  have  to  swing  beneath  the  sterigmata.  On  the 
assumption  of  passive  fall  it  seemed  impossible  to  imagine  how  the 
adhesive  spores  could  be  liberated.  Before  any  observations  were 
made,  therefore,  it  appeared  to  me  highly  probable  that  in  some 
manner  the  spores  must  be  projected  for  a  short  distance  straight  out 
from  the  hymenium  in  which  they  are  produced.  This  deduction 
has  been  verified  in  various  ways.  My  observations  seem  to  indicate 
that  violent  spore-projection  is  of  general  occurrence  throughout  the 
Hymenomycetes. 

So  far  as  I  am  aware,  hitherto  Brefeld  alone  has  made  observa- 
tions on  the  separation  of  spores  from  the  basidia.  In  the  case  of 
Amanita  muscaria 1  he  simply  says,  "  In  diese  [the  spaces  between 
the  gills]  werden  die  Sporen  durch  schwache  Ejaculation  geworfen 
und  fallen  dann  zu  Boden."  In  a  footnote  in  his  account  of  the 
life-history  of  Coprinus  stercorarius?  he  states  that  the  spores  are 
shot  outwards  in  consequence  of  the  bursting  of  the  sterigmata.  He 
believes  himself  to  have  seen  small  drops  left  on  the  sterigmata,  and 
also  on  the  spores  after  spore-discharge,  and  states  that  all  four 
spores  are  shot  off  from  a  basidium  simultaneously.  With  regard  to 
violent  spore-ejaculation  being  a  fact,  I  am  in  entire  agreement  with 
Brefeld,  but  am  unable  to  confirm  his  description  of  the  process  in 
detail.  The  spores,  so  far  as  my  experience  with  several  species  of 

1  Brefeld,  Botanische  Untersnchungen  iiber  Schimmelpilze,  III.  Heft,  p.  132. 

2  Brefeld,  loc.  cit.,  pp.  65,  66. 


THE   VIOLENT   PROJECTION   OF  SPORES 


135 


Coprinus  and  of  many  other  genera  goes,  are  never  shot  off  simul- 
taneously. I  have  also  not  been  able  to  obtain  any  evidence  that 
the  spores  are  projected  forwards  owing  to  ejaculation  of  the  contents 
of  the  basidia.  The  mechanism  of  spore-discharge,  however,  will  be 
discussed  more  conveniently  in  the  next  chapter. 

Several  methods  have  been  used  to  determine  whether  or  not  the 
spores  are  shot  off  the  sterigmata.  The  first  one,  which  seemed  for 
some  time  to  give  convincing  evidence  of  spore-projection,  led  to  the 
discovery  of  an  unexpected  optical  illusion. 

Method  I. — The  first  method  employed  for  observing  spore-fall 
microscopically  was  that  of  placing  hymenial  surfaces  in  vertical 
planes  and  observing  them  from 
above  with  an  ordinary  upright 
microscope. 

Through  the  middle  of  some 
of  the  hymenial  tubes  of  a  freshly 
grown  fruit- body  of  Polyporus 
squamosus,  a  transverse  section 
1-2  mm.  thick  was  made  (Fig.  47). 
This  was  then  placed  on  a  glass 
slide,  covered  with  a  cover-glass, 
and  looked  down  upon  from  above 
with  the  low  power  of  the  micro- 
scope. Immediately  the  remark- 
able fact  was  observed  that  the  spores  were  apparently  being  shot 
outwards  from  the  hymenium  towards  the  middle  of  the  tubes. 
Apparently  one  could  see  them  taking  part  of  their  curved  and  out- 
ward course  through  the  air.  They  were  also  seen  to  settle  below  on 
the  glass  slide  on  the  average  at  a  distance  of  0'1-0*2  mm.  (6-20 
times  their  own  length)  from  the  hymenium.  In  this  way  the  spores 
collected  in  a  zone  about  0'5  mm.  wide  around  the  base  of  each  tube. 
In  the  course  of  a  few  minutes  I  watched  the  discharge  of  hundreds 
of  spores.  Not  only  to  myself,  but  to  others,  the  apparent  bombard- 
ment of  the  spores  into  the  lumina  of  the  tubes  seemed  to  afford 
clear  and  convincing  proof  of  the  violent  projection  of  the  spores 
from  the  basidia. 

Similar  observations  to  those  just  recorded  were  then  made  upon 


FIG.  47.— Diagram  to  show  the  shape  of 
a  transverse  section  through  the  hy- 
menial tubes  of  Polyporus  squamosus. 
About  6  times  natural  size. 


136  RESEARCHES   ON   FUNGI 

other  species  of  Polyporus,  and  also  upon  species  of  Polystictus, 
Dsedalea,  and  Boletus.  The  hymenial  tubes  of  many  members  of  the 
Polyporeae  are  extremely  narrow.  Thus  with  the  aid  of  the  drawing 
apparatus  and  a  stage  micrometer,  it  was  found  that  the  diameters 
of  the  tubes  at  the  mouths  were  on  the  average :  for  Polyporus 
hirsutus,  O'S-0'4  mm. ;  for  Fomes  vegetus,  G'15-0'2  mm. ;  for 
Fomes  igniarius,  O'lo  mm. ;  and  for  Polystictus  versicolor,  0-2- 
0'25  mm.  In  Polyporus  hirsutus  and  Polystictus  versicolor,  for 
which  species  alone  fresh  material  was  available,  the  spores  seemed 
to  be  bombarded  from  the  hymenium  just  as  in  the  case  of  Polyporus 
squamosus.  They  appeared  to  be  projected  outwards  from  the 
hymenium  and  were  seen  to  descend  near  the  centres  of  the  tubes, 
at  the  mouths  of  which  they  collected  in  heaps.  Polyporus  hirsutus 
had  tubes  in  the  centre  part  of  its  fruit-body  2  cm.  long.  However, 
by  making  transverse  sections  at  different  heights  it  was  observed 
that  the  spores  were  discharged  throughout  the  whole  length  of  a 
tube.  For  Polystictu»  versicolor  the  tubes  were  often  only  0-2  mm. 
wide.  Yet  even  in  these  the  spores  seemed  to  be  shot  outwards 
from  the  hymenium.  They  appeared  to  travel  a  distance  of  about 
01  mm.  toward  the  middle  of  the  tubes  before  the  horizontal  velocity 
had  been  reduced  to  zero. 

The  species  of  Boletus  investigated  and  the  diameters  of  their 
pores,  as  given  by  Massee,1  were  as  follows:  Boletus  chrysenteron, 
1-1-5  mm.;  B.  felleus,  up  to  1  mm.;  B.flavus,  §-1  mrn. ;  B.  subto- 
mentosus,  §-1  mm. ;  B.  scaber,  O'5-l  mm. ;  B.  badius,  O'5-l  mm. 
Here,  again,  sections  1-2  mm.  high  were  taken  transversely  through 
the  hymenial  tubes,  and  looked  into  from  above  with  the  low  power 
of  the  microscope.  In  each,  again,  the  spores  were  apparently  shot 
off  from  the  hymenium  into  the  tubes.  In  the  wider  tubes  the  spores 
were  seen  to  collect  at  the  mouths  in  a  zone  around  the  walls,  and  in 
the  narrower  ones  they  gradually  formed  a  central  heap.  The  im- 
pression gained  was  that  the  spores  were  projected  horizontally  on 
the  average  O-2-O'l  mm.,  or  about  the  same  distance  as  for  Polyporus 
squamosus.  Dasdalea  unicolor  (a  very  common  fungus  at  Winnipeg) 
behaved  like  the  Boleti. 

In  order  to  observe  the  fall  of  spores  in  members  of  the  Agari- 
1  G.  Massee,  British  Fungus-Flora,  1892,  vol.  i. 


THE   VIOLENT   PROJECTION   OF  SPORES         137 

cineae,  tangential  sections  about  1-2  mm.  thick  were  made  through 
the  pilei,  so  as  to  cut  the  gills  transversely.  The  sections  were  then 
placed  on  a  microscope  slide,  by  which  means  the  hymenial  surfaces 
took  up  a  vertical  position  (Fig.  48).  Sometimes  the  sections  were 
placed  in  a  glass  cell  closed  with  a  cover-glass,  but  this  precaution  for 
keeping  off  air-currents  was  usually  found  unnecessary  in  a  quiet 
room  where  the  air  was  still.  The  spores  appeared  to  be  violently 
projected  from  the  hymeniurn  into  the  spaces  between  the  gills  in  all 
the  species  which  were  examined.  As  in  the  case  of  Polyporus 
squamosus,  however,  only  part  of  the  path  of  each  spore  could  be 
observed,  owing  to  the  fact  that  only  one  plane  can  be  focussed  at 
one  time  by  the.  microscope.  The  discharge  of  the  spores  could 
usually  be  detected  almost  immediately  the  section  had  been  made, 
and  continued  for  some  minutes 
until  loss  of  water  from  the  gills 
interfered  with  the  process.  In 
small,  closed  glass  chambers, 
where  loss  of  water  vapour  was 
prevented,  the  discharge  of 
spores  continued  in  some  in- 
stances  for  several  hours.  The 

Spore  zone  of  discharged  Spores  with  gills.     The  hymenial  surfaces  are 

c  vertical.     About  4  times  natural  size. 

on  the  glass  slide  between  two 

gills  and  adjacent  to  the  base  of  each  was  in  most  cases  about 
0*2  mm.  wide.  The  impression  was  gained  that  the  spores  had  been 
projected  about  O'l  mm.  before  the  horizontal  motion  was  destroyed. 
The  Agaricinea3  used  as  material  for  these  observations  consisted  of 
thirty-one  species  common  in  the  Midlands  of  England,  and  included 
in  the  following  genera:  Psalliota,  Stropharia,  Anellaria,  Galera, 
Amanitopsis,  Amanita,  Lactarius,  Russula,  Panreolus,  Psilocybe, 
Colly bi a,  Cantharellus,  Laccaria,  Hygrophorus,  Nolanea,  Hypholoma, 
Marasmius,  Entoloma,  Mycena,  and  Armillaria. 

The  first  method  of  observing  spore-fall  with  the  microscope 
in  the  Polyporeae  and  Agaricinese  appeared  to  yield  two  facts  in 
favour  of  the  supposition  that  the  spores  are  violently  discharged 
from  the  sterigmata:  (I)  The  spores  could  apparently  be  seen 
travelling  horizontally  away  from  the  basidia,  and  (2)  the  spores 


138 


RESEARCHES   ON  FUNGI 


settled  some  distance  from  the  vertically-placed  hymenium.  The 
latter  fact  I  regard  as  good  evidence  of  spore-projection,  but  the 
former,  which  for  some  time  seemed  to  yield  convincing  proof  of 
the  phenomenon,  has  been  found  by  subsequent  investigation  to 
be  misleading  and  based  upon  a  curious  optical  illusion.  As  a 
result  of  further  observations  and  calculations  it  can  be  shown 
that  the  spores  are  really  projected  from  the  basidia  with  a  high 
velocity,  but  nevertheless  it  is  most  improbable  that  one  should 
observe  directly  the  horizontal  motion  of  a  spore  because  it  is 

performed  too  rapidly. 
The  apparent  travelling 
outwards  of  a  spore 
from  the  vertically- 
placed  hymenium, 
which  one  can  observe 
so  easily  in  Agaricinese 
and  Polyporese,  is  really 
no  travelling  outwards 
at  all.  The  spores,  when 
seen  in  motion,  are  in 
reality  falling  vertically. 
For  some  months  this 
illusion  deceived  me, 
as,  indeed,  it  had  de- 


M 


N 


^? 


FlG.  49.— Diagram  of  a  tiny  cylinder  MN  on 
slide  S,  viewed  from  above  in  the  direction 


the 


arrow  O  with  the  low  power  of  the   microscope. 
ABCD   is   a  section  of  the  cylinder  within   the 


range  of  focus.  X  and  Y  show  the  paths  of  two 
spores  falling  vertically.  To  the  right  is  shown 
how  the  section  and  the  paths  of  the  spores  appear 
to  the  observer. 


ceived  others  to  whom 
I  had  shown  it.  How- 
ever, the  possibility  of  the  apparent  fact  of  horizontal  movement 
of  the  spores  being  in  some  way  deceptive,  caused  me,  after  a  while, 
to  make  a  careful  study  of  the  appearance  of  vertical  surfaces 
under  the  microscope. 

A  tiny  brass  cylinder  was  constructed,  placed  upright  on  a  glass 
slide,  and  observed  from  above  with  the  low  power  of  the  microscope. 
It  was  found  that,  wherever  placed  in  the  field,  any  part  of  the 
vertical  surface  observed  appeared  to  slope  at  an  angle  from  the 
vertical.  The  result  of  the  observations  may  best  be  made  clear 
by  means  of  a  diagram  (Fig.  49).  Let  MN  be  the  cylinder  standing 
vertically  upright  on  the  glass  slide  S,  and  let  the  arrow  O  indicate 


THE   VIOLENT   PROJECTION   OF  SPORES 


139 


II 


B 


the  direction  in  which  the  cylinder  is  viewed  with  the  microscope. 
Let  A  B  C  D  be  a  section  of  the  cylinder  placed  within  the  range 
of  focus.  Then  to  the  observer  the  section  will  have  the  appearance 
of  a  truncated  cone,  abed.  The  truly  vertical  sides  of  the  section 
of  the  cylinder  will  appear  inclined  as  shown  in  the  figure.1  Now 
let  the  arrows  X  and  Y  indicate  the 
truly  vertical  paths  of  two  spores  falling 
parallel  to  the  sides  AB  and  CD  of  the 
cylinder.  Then,  when  observed  with  the 
microscope,  the  course  of  the  spores  will 
appear  to  be  as  indicated  by  the  arrows 
x  and  y,  i.e.  the  illusion  will  be  created 
that  the  spores  are  moving  more  or  less 
horizontally  outwards  from  the  cylinder. 
The  apparent  bombardment  of  the 
spores  into  the  spaces  between  the  gills, 
which  one  sees  on  looking  vertically 
downwards  upon  a  section  like  that  in 
Fig.  48,  may  now  be  explained.  Let 
A  A  in  Fig.  50  represent  a  vertical  section 
taken  transversely  through  three  of  the 
gills,  and  let  the  arrows  placed  parallel 
to,  and  at  a  little  distance  from,  their 
vertical  sides,  represent  the  true  paths 
of  six  spores  falling  vertically.  Then,  as 
shown  at  BB,  when  the  low  power  ob- 
jective of  the  microscope  is  placed  in  the 
position  of  the  arrow  O,  one  apparently 
observes  spores  being  shot  outwards  from 
both  sides  of  the  gill  immediately  below, 
and,  when  one  observes  in  the  direction 


FIG.  50.— Above  at  AA  is  shown 
a  transverse  and  vertical  section 
through  three  gills  of  a  piece 
of  a  pileus  like  that  in  Fig.  48. 
When  observed  from  above  in 
the  directions  of  the  arrows  O, 
P,  and  Q,  the  range  of  focus 
is  supposed  to  be  between  the 
dotted  lines.  The  four  arrows 
between  the  gill-sections  indi- 
cate the  paths  of  four  spores 
falling  parallel  to  and  about  one- 
tenth  of  a  millimetre  from  the 
hymenial  surfaces.  Below  at 
BB  is  shown  the  apparent  shape 
of  the  parts  of  the  gills  in  focus 
and  the  apparent  paths  of  the 
spores.  The  latter,  although 
falling  vertically,  appear  to  be 
shot  outwards  from  the  hy- 
menial surfaces  into  the  spaces 
between  the  gills. 


indicated  by  either  of  the  arrows  P  or  Q,  one  apparently  sees  the  spores 
being  shot  outwards  from  two  gills  into  the  interlamellar  spaces. 

1  The  explanation  of  the  phenomenon  seems  to  be  due  to  the  fact  that  the 
area  of  the  objective  is  large  compared  with  diameter  of  the  cylinder,  so  that 
different  parts  of  the  objective,  as  it  were,  can  see  different  parts  of  the  cylinder. 
With  the  low  power  of  the  microscope  one  can  see  simultaneously  both  sides  of 
an  ordinary  glass  slide  placed  vertically. 


140  RESEARCHES   ON  FUNGI 

It  is  now  clear  to  me  that  the  apparent  shooting  out  of  spores 
from  the  vertically-placed  hymenium  in  the  many  Agaricinese  and 
Polyporese  observed  by  my  first  method  is  simply  an  illusion. 
During  the  apparent  bombardment  of  hundreds  of  spores  into  a 
cross  section  of  a  tube  of  Polyporus  squamosus,  or  into  the  spaces 
between  two  gills  in  a  Mushroom  (which  one  sees  in  looking  down 
upon  such  sections  as  those  represented  in  Figs.  47  and  48),  one 
does  not  really  see  a  single  spore  performing  any  part  of  its 
horizontal  motion.  The  spores  are  falling  vertically  as  soon  as 
ever  perceived.  By  methods  to  be  described  in  Chapter  XVII.  it 
has  been  found  that  for  Amanitopsis  vaginata  the  total  horizontal 
distance  to  which  the  spores  are  projected,  namely,  about  0'2  mm., 
is  accomplished  in  approximately  only  4^  second,  and  that  the 
initial  velocity  with  which  each  spore  is  shot  forward  is  about 
400  mm.  per  second.  From  a  consideration  of  these  remarkable 
figures,  and  also  the  fact  that  the  spores  must  be  considerably 
magnified  in  order  to  be  seen  at  all,  it  seems  to  me  very  improbable 
that  the  human  eye,  aided  as  it  must  be  by  the  microscope,  will 
ever  be  able  to  detect  the  horizontal  motion  of  a  spore.  Whether 
or  not  it  is  possible  to  do  so  must  be  left  to  the  experimental 
psychologist.  That  the  downward  motion  of  a  spore,  which  is 
performed  at  a  constant  speed  in  response  to  gravity,  should  be 
observed  as  described  is  easily  understood,  for  it  is  performed 
relatively  much  more  slowly  and  for  a  much  longer  distance  than 
the  horizontal  motion.  In  the  case  of  Amanitopsis  vaginata  the 
terminal  vertical  velocity  is  only  about  5  mm.  per  second.  In 
most  other  species,  where  the  spores  are  smaller,  the  velocity  is 
usually  only  1-2  mm.  per  second.1  These  theoretical  considera- 
tions, which  it  has  been  necessary  to  introduce  in  this  place  in 
order  to  explain  the  results  of  observations  Avith  Method  I.,  will 
doubtless  become  clearer  to  the  reader  when  the  curious  nature 
of  the  "sporabola"  has  been  discussed  in  a  subsequent  chapter. 

Observations,  with  the  special  object  of  seeing  the  horizontal 

flight  of  particular   spores  on  leaving  the  sterigtnata,  were  made 

with  sections  of  Polyporus  squamosus  like  that  in  Fig.  47  on  several 

occasions,  but   they  gave  only  negative   results.     With  a  vertical 

1    Vide  infra,  Chaps.  XV.  and  XVI. 


THE   VIOLENT   PROJECTION   OF   SPORES 


141 


microscope  a  ripe  spore  on  its  horizontal  sterigma  was  carefully 
watched  until  it  Avas  discharged.  One  mo- 
ment it  was  in  view :  the  next  it  had  dis- 
appeared, but  in  what  direction  could  not 
be  detected.  The  eye  had  not  been  able  to 
follow  the  motion. 

Method  II. — The  second  method  em- 
ployed to  determine  whether  or  not  violent 
spore-projection  takes  place  was  as  follows: 
A  piece  of  a  gill,  4-5  mm.  high  and  2-3 
mm.  broad,  was  cut  from  a  ripe  fruit-body 
of  Amanitopsis  vaginata  and  placed  in  a 
vertical,  but  inverted,  position  on  a  tiny 
glass  shelf  in  a  vertically-disposed  compressor 
cell.  A  horizontal  microscope,  with  a  magni- 
fication of  about  25  diameters,  was  then 
employed  to  observe  the  fall  of  spores  from 
the  piece  of  the  gill  when  seen  end-wise  (cf. 
Plate  IV.,  Fig.  29).  The  gill  segment  thus 
came  to  be  so  placed  that  the  sides  bearing 
the  hymenium  were  inclined  to  the  vertical, 
as  shown  in  Fig.  51.  The  hymenium,  there- 
fore, looked  very  slightly  upwards.  Usually 
it  was  found  convenient  to  concentrate  the 
attention  on  one  side  of  the  gill,  and  in  all 
cases,  by  tilting  the  compressor  cell  held  in 
a  clamp,  the  side  in  question  was  made  to 
incline  distinctly  upwards  at  a  slight  angle 
from  the  vertical.  It  was  argued  that,  if  the 
adhesive  spores  only  drop  off  the  sterigmata 
passively,  they  would  never  be  seen  in  the 
air,  whereas,  if  indeed  they  are  projected 
violently  outwards,  although  one  might  not 
be  able  to  see  them  in  their  horizontal  flight, 
yet  one  should  often  be  able  to  see  them  falling  vertically  at  a  little 
distance  from  the  gill  surface. 

On   actually  making  the   observations,  it  was   found   that   the 


FlG.  51. — Diagram  show- 
ing a  piece  of  a  gill 
inverted  and  placed  on 
a  tiny  horizontal  shelf, 
AA,  in  a  vertically- 
disposed  compressor  cell. 
The  piece  of  gill  is  seen 
edgewise  with  the  hori- 
zontal microscope.  H  is 
the  hymenium.  S,  S, 
show  the  paths  of  the 
spores  when  seen  falling. 
The  spores  first  come  into 
view  about  one-tenth  of  a 
millimetre  from  the  hy- 
menium. About  20  times 
natural  size. 


1 42  RESEARCHES   ON  FUNGI 

spores  came  suddenly  into  view  at  a  distance  of  O1-O2  mm.  from 
the  gills.  As  soon  as  seen,  the  spores  were  falling  vertically  at  a 
constant  speed.1  The  diagram,  Fig.  51,  shows  the  courses  of  a  few 
spores  as  seen  with  the  horizontal  microscope.  These  observations 
seem  to  me  to  afford  conclusive  proof  of  violent  spore-projection. 
They  ma}7  be  repeated  without  difficulty.  One  may  have  to  wait 
a  few  seconds  or  minutes  before  a  spore  springs  into  view,  but  this 
is  merely  a  question  of  patience.  The  species  used  for  these  ob- 
servations, in  addition  to  Amanitopsis  vaginata,  were:  Psalliota 
campestris,  Marasmius  oreades,  and  Polypwus  squamosus.  For 
the  Polyporus  a  piece  of  the  wall  between  two  hymenial  tubes 
took  the  place  of  a  piece  of  gill. 

The  horizontal  distance  from  the  hyinenium,  at  which  a  spore, 
when  first  perceived,  appeared  to  be,  was  compared  with  the  dis- 
tance between  tiny  irregularities  on  a  silk  thread  of  the  Ramsden 
eyepiece  of  the  horizontal  microscope.  The  latter  distance  was 
then  carefully  measured  with  a  standard  micrometer  scale.  After 
a  number  of  observations  had  been  made  in  each  case,  the  con- 
clusion was  arrived  at  that  the  spores  of  Amanitopsis  vaginata 
are  often  shot  to  a  horizontal  distance  of  i  mm.,  and  that  those 
of  the  other  three  species  are  often  shot  T\j-  mm.  and  sometimes 
a  little  further. 

Method  III. — The  third  method  employed  for  demonstrating 
the  violent  projection  of  spores  from  the  sterigmata  is  perhaps 
the  most  conclusive  of  all.  It  can  be  carried  out  most  certainly 
and  easily  with  fruit-bodies  of  the  Coprini.  Coprinus  plicatilis 
was  made  chief  use  of  in  these  experiments,  but  C.  comatus 
and  C.  micaceus  gave  similar  results.  One  takes  a  gill  that 
is  shedding  spores  and  lays  it  flat  in  a  closed  compressor  cell,  and 
observes  it  from  above  with  the  low  power  of  an  ordinary  micro- 
scope. Under  these  conditions  the  basidia  are  pointing  upwards. 
One  can  then  very  readily  observe  the  disappearance  of  the  spores 
from  the  sterigmata  near  the  "  deliquescing "  gill  edge,  for  it  is 
here  and  here  alone  in  the  Coprini  that  active  discharge  of  spores 
takes  place  (Plate  II.,  Fig.  12).  If  one  focusses  a  plane  at  a  little 

1  The  air  in  a  compressor  cell  is  practically  quite  still.  The  spores  fall  verti- 
cally in  it,  and  are  not  carried  about  by  convection  currents. 


THE   VIOLENT  PROJECTION   OF   SPORES         143 

distance  above  the  plane  of  the  hymenium,  so  that  the  basidia 
are  just  out  of  view,  one  finds  that  spores  spring  into  view  and 
immediately  disappear  again.  This  proves  conclusively  that  the 
spores  have  been  projected  violently  upwards  from  the  sterigmata. 
The  fine  adjustment  screw  of  the  microscope  was  carefully  cali- 
brated by  the  glass  plate  method,  and  it  was  then  found  by  measure- 
ment with  it  that  in  the  case  of  Coprinus  plicatilis  the  spores 
were  projected  upwards,  so  that  they  came  into  view  in  a  plane 
O08-O12  mm.  above  the  plane  of  the  spores  on  the  sterigmata. 

It  has  been  found  possible  to  observe  the  upward  projection  of 
spores  in  the  Mushroom,  and  also  in  a  species  of  Psilocybe.  In 
these  cases,  however,  observations  can  only  be  made  with  consider- 
able difficulty.  In  the  ,Coprini  the  spores  in  a  zone  parallel  with, 
and  adjoining,  the  deliquescing  gill  edge  are  all  being  discharged 
almost  simultaneously  (Plate  II.,  Fig.  12).  The  gills  of  Coprini  are 
also  very  thin  and  allow  ample  light  to  pass  through  them.  In 
all  other  species  of  Agaricinese,  however,  the  spores  are  discharged 
irregularly  over  the  whole  surface  of  a  gill  and  there  is  no  special 
region  of  activity.  Adjacent  basidia  are  in  very  various  stages  of 
development.  When  one  looks  down  on  a  piece  of  gill  of  one  of 
these  fungi,  one  but  rarely  sees  the  spores  disappear  from  a  basidium. 
This  is  due  to  the  fact  that  the  ripe  basidia  are  relatively  far  apart. 
The  gills  are  also  much  thicker  than  in  the  Coprini  and  allow  but 
little  light  to  pass  through  them. 

The  observations  on  the  Mushroom  were  carried  out  in  the 
following  manner.  A  fresh  specimen  was  obtained  from  a  field 
and  part  of  one  of  the  pink  gills  placed  flat  in  a  closed  compressor 
cell.  The  latter  was  then  placed  on  the  stage  of  the  microscope 
and  this  tilted  to  an  angle  of  about  45°.  The  tilting  ensured  that 
if  a  spore  was  shot  off  a  sterigma  in  the  field  of  view,  it  would 
remain  longer  in  view  than  it  would  if  the  microscope  were  vertical. 
A  plane  situated  a  short  distance  above  the  hymenium  was  focussed 
so  that  one  could  not  see  any  of  the  basidia  distinctly.  After 
several  hours  of  watching,  on  three  separate  occasions  a  spore  was 
clearly  seen  to  come  into  view  in  the  plane  above  the  hymenium 
and  to  travel  a  little  way  across  the  field  of  view  before  disappearing. 
The  only  explanation  of  these  observations  seems  to  be  that  the 


i44  RESEARCHES   ON  FUNGI 

spores  had  been  shot  off  the  sterigmata  just  as  in  the  Coprini.  A 
species  of  Psilocybe  yielded  a  similar  result. 

Method  IV. — A  piece  of  a  gill  of  a  Mushroom  was  placed  flat 
in  a  closed  compressor  cell  and  observed  from  above  with  an 
ordinary  vertical  microscope.  An  endeavour  was  made  to  see  the 
spores  leave  the  sterigmata  of  individual  basidia.  It  was  argued 
that,  if  the  spores  merely  fall  passively  from  the  sterigmata,  after 
liberation  they  ought  to  lie  below  their  respective  sterigmata, 
whereas,  if  they  are  discharged  violently,  they  should  often  take 
up  other  positions. 

Apparently  ripe  basidia  were  focussed  and  watched.     After  some 

D    _ 


jj  w  tx  s? 


FIG.  52. — The  successive  and  violent  discharge  of  the  four  spores  from  the 
basidium  of  Psalliota  campestris.  Part  of  a  gill  was  laid  flat  in  a  compressor 
cell.  The  basidium  looked  upwards  and  was  observed  from  above.  X  the 
basidium,  with  its  four  ripe  spores.  The  appearance  of  the  basidium  imme- 
diately after  the  discharge  of  spores  1,  2,  3,  and  4  is  shown  at  A,  B,  C,  and 
D  respectively. 

hours  had  been  spent  at  this  task,  a  basidium  was  seen  to  discharge 
all  its  spores.  Sketches  were  made  after  the  discharge  of  each 
spore  and  are  reproduced  in  Fig.  52.  When  one  watches  the  dis- 
charge of  a  spore,  all  that  one  can  see  is  that  the  spore  suddenly 
disappears  from  its  sterigma  and  immediately  appears  again  in  a 
new  position  on  the  hymeniurn.  In  Fig.  52,  X  shows  the  appear- 
ance of  the  four  spores  on  the  basidium  before  discharge,  and 
A,  B,  C,  and  D  illustrate  what  was  seen  immediately  after  the 
discharge  of  spores  Nos.  1,  2,  3,  and  4  respectively.  It  is  clear 
that  the  spore  No.  2  (B)  must  have  jumped  over  No.  4  to  get 
into  the  position  it  came  to  occupy  after  discharge.  Similarly, 
No.  4  (D)  must  have  jumped  over  No.  3.  A  study  of  this  case 


THE  VIOLENT  PROJECTION  OF  SPORES         145 

and  many  others,  where  only  the  last  spore  or  the  remaining  two 
or  three  spores  were  observed  to  be  discharged,  has  convinced  me 
that  the  spores  when  liberated  must  be  shot  upwards  for  a  little 
distance  before  falling  on  to  the  hymenium.  Doubtless  the  spores 
were  shot  not  quite  vertically  upwards,  but  nearly  so.  Hence  the 
various  positions  of  the  spores  after  settling. 

In  the  Coprini,  it  is  exceedingly  easy  to  observe  the  discharge  of 
spores  from  the  basidia  near  the  edge  of  a  "  deliquescing  "  gill.  As 
before,  it  is  necessary  to  place  the  gill  or  piece  thereof  flat  in  a  closed 
compressor  cell  to  prevent  too  rapid  loss  of  water  and  consequent 
collapse  of  the  basidia.  With  the  low  power  of  the  microscope  one 
can  then  observe  large  numbers  of  basidia  actively  shedding  their 
scores  (Plate  II.,  Fig.  12).  The  phenomenon  has  quite  a  fascination 
of  its  own.  The  spores,  after  disappearing  from  the  sterigmata,  very 
frequently  immediately  reappear  on  the  hymenium  at  some  distance 
from  the  basidia  on  which  they  have  been  developed.  There  is 
no  essential  difference  between  the  Mushroom  and  the  Coprini  in 
regard  to  what  one  sees  by  using  Method  IV.  Fig.  52  might 
equally  well  apply  to  the  basidium  of  a  Coprinus  comatus  or 
C.  plicatilis. 

One  fact  which  is  yielded  by  the  above  observations,  and  has  an 
important  bearing  in  explaining  the  mechanism  of  spore-discharge, 
is  that  the  four  spores  of  a  basidium  are  not  shot  off  their  sterigmata 
simultaneously  but  successively.  The  succession  of  discharges  in 
the  particular  instance  shown  in  Fig.  52  occupied  twenty  minutes. 
There  was  an  interval  of  a  few  minutes  after  each  one  before  the 
next  took  place.  It  is  quite  certain  that  usually  the  four  spores  of 
a  basidium  are  not  discharged  together.  When  one  looks  at  the 
hymenium  of  a  Mushroom  gill  in  face  view,  it  is  easy  to  observe  that 
many  of  the  ripe  basidia  have  only  one,  two,  or  three  spores  left  upon 
them.  In  many  instances  the  successive  discharge  of  two  or  three  of 
the  spores  was  actually  watched.  In  Coprinus  comatus  one  can 
make  similar  observations  with  great  ease.  I  have  watched  hundreds 
of  basidia  discharge  their  spores  in  this  species,  yet  never  once  have 
I  seen  all  four  spores  of  a  basidium  discharged  together.  Here,  as  in 
the  Mushroom,  the  four  spores  of  a  basidium  disappear  from  their 

sterigmata  one  by  one,  in   the  course  of  one  or  a   few  minutes. 

K 


146 


RESEARCHES   ON  FUNGI 


I 


The  same  results  were  obtained  with  Coprinus  pUcatiUa  and 
C.  micaceus.  In  the  already-mentioned  footnote  to  Brefeld's 
description  of  C.  stercorarius,  it  is  stated  that  the  spores  are  all 
discharged  simultaneously.  Although  I  have  not  had  an  oppor- 
tunity of  examining  this  species,  I  think  it  highly  probable  that  it 
discharges  its  spores  in  the  same  manner  as  other  Coprini,  and  that 
Brefeld's  statement  will  not  be  corroborated  by  further  observation. 

Whilst  using  Method  I.  it  was  often  easy  to  observe  single  ripe 
basidia  and  to  watch  the  disappearance  of  some  of  the  spores.    Thus, 

in  the  case  of  Poly- 
porus  squamosus,  in 
one  instance  three 
spores  left  a  basi- 
diuin  at  intervals  of 
twenty  seconds, 
whilst  the  fourth 
remained  on  its 
sterigma  for  some 
minutes  afterwards 
and  was  not  seen  to 
disappear.  In  an- 
other instance  two 
of  the  four  spores 
left  a  basidium  with- 
in a  few  seconds  of 
one  another.  A  large 
number  of  observa- 


FIG.  53. — Diagram  showing  the  appearance  of  part  of  the 
hymenium  at  the  base  of  a  section  of  a  hymenial  tube 
of  Polyporus  squamosus  (cf.  Fig.  47.  p.  135).  The  arrow 
indicates  the  direction  of  observation.  A  basidium 
bearing  four  ripe  spores  and  the  top  of  the  glass  slide 
were  included  in  the  range  of  focus.  The  figure  shows 
the  position  of  one  of  the  spores  on  the  glass  slide 
after  being  discharged  to  six  times  its  own  length  from 
the  basidium. 


tions,  obtained  by  using  Methods  I.  and  IV.,  have  convinced  me  that 
in  very  many  species  the  spores  are  discharged  from  a  ripe  basidium, 
not  simultaneously,  but  successively  one  after  the  other.  It  seems 
to  me  highly  probable  that  this  is  a  general  rule  throughout  the 
Hymenomycetes. 

Method  V. — A  transverse  section  through  the  hymenial  tubes  of 
Polyporus  squamosus  (Fig.  47)  was  made  and  placed  on  a  glass  slide 
in  the  same  manner  as  was  done  for  Method  I.  The  basidia  thus 
came  to  occupy  their  normal  horizontal  positions.  The  discharge  of 
spores  was  watched  with  the  ordinary  vertical  microscope.  I  con- 


THE   VIOLENT   PROJECTION   OF  SPORES         147 

centrated  my  attention  upon  a  ripe  basidium  which  projected 
horizontally  from  the  hymenium  in  one  of  the  tubes  at  a  very  short 
distance  above  the  glass  slide  (Fig.  53).  So  near  was  the  basidium 
to  the  slide  that  I  was  able  to  have  both  spores  and  glass  surface 
within  the  range  of  focus  at  the  same  time.  After  I  had  watched  for 
a  long  time,  one  of  the  spores  suddenly  left  the  basidium  and  became 
deposited  on  the  glass  slide  some  six  times  its  length  from  the 
basidium.  It  had  therefore  been  shot  along  just  above  the  glass 
surface  for  a  distance  of  6  x  13  /^  or  0*078  mm.  The  observation  just 
recorded,  although  the  only  one  of  its  kind  that  I  have  been  able  to 
make,  seems  to  give  another  convincing  proof  of  the  fact  of  violent 
spore-projection.  The  actual  movement  of  the  spore  from  the 
basidium  to  its  place  of  rest  on  the  glass  slide  was  not  seen,  although 
I  was  watching  with  concentrated  attention  for  the  express  purpose 
of  observing  it.  However,  certain  mathematical  considerations  soon 
to  be  treated  of,  indicate  that  it  is  highly  improbable,  if  not  im- 
possible, that  one  should  perceive  the  horizontal  motion,  however 
carefully  one  might  make  one's  observations. 


CHAPTER  XII 

THE  MECHANISM  OF  SPORE-DISCHARGE 

IN  the  last  chapter  it  was  shown  that  the  spores  of  Hymenomycetes 
are  discharged  frorn  the  sterigmata  in  a  violent  manner.  The 
mechanism  by  which  this  process  is  brought  about  will  now  be 
discussed. 

Brefeld,1  in  a  footnote  to  his  account  of  the  life-history  of 
Coprinus  stercorarius,  has  stated  that  all  the  four  spores  of  a 
basidium  are  discharged  simultaneously,  and  that,  immediately 
after  a  discharge,  small  drops  are  left  upon  the  vacant  sterig- 
mata and  also  on  the  spores.  He  came  to  the  obvious  and 
apparently  sufficient  conclusion  that  the  spores  are  shot  forward 
on  account  of  the  bursting  of  the  sterigmata  and  the  ejacu- 
lation of  their  contents.  However,  after  studying  the  discharge 
of  spores  in  several  species  of  Coprinus,  as  well  as  in  Polyporus 
squamosus,  Psalliota  campestris,  &c.,  I  find  myself  unable  to 
confirm  Brefeld's  observations.  The  facts  brought  forward  in 
the  last  chapter 2  afford  conclusive  proof  that  the  four  spores 
of  a  basidium  are  discharged  not  simultaneously  but  successively. 
By  applying  my  Method  IV.3  to  the  examination  of  a  gill 
margin  (Plate  II.,  Fig.  12)  of  a  ripe  Coprinus  fruit-body,  any  one 
may  observe  the  successive  discharge  of  the  four  spores  from 
scores  of  basidia  in  a  few  minutes.  The  shooting  off  of  all  four 
spores  usually  occupies  from  about  one  to  several  minutes.  At  the 
moment  of  discharge  of  the  spores  from  the  basidia  of  Coprinus 
comatus,  Polyporus  squamosus,  &c.,  I  have  endeavoured  to  observe 
drops  on  the  vacant  sterigmata,  but  without  success ;  nor,  by  using 
my  Method  I.,4  have  I  been  able  to  detect  drops  on  any  spores  as 

1  Brefeld,  loc.  cit.  2  Under  Method  IV. 

3  Chap.  XI.  «  Chap.  XI. 

148 


•< 


THE  MECHANISM  OF  SPORE-DISCHARGE        149 

soon  as  they  have  settled  on  glass  immediately  after  leaving  the 
basidia.1 

For  the  purpose  of  finding  out  the  mechanism  of  spore- 
discharge,  a  transverse  section  through  the  hymenial  tubes  of 
Polyporus  squamosus  was  cut,  and  the  horizontal  basidia  looked 
down  upon  with  the  vertical  microscope  as  already  described  for 
Methods  I.  and  V.2  A  particular  basidium,  bearing  four  ap- 
parently ripe  spores,  was  carefully  focussed.  After  a  watch  had 
been  kept  for  some  time,  one  of  the  spores  suddenly  disappeared. 
The  end  of  the  sterigma  left  vacant  was  then  seen  to  be  pointed  and 
entirety  devoid  of  any  drop  of  fluid  (cf.  Fig.  53,  p.  146  ;  also  Plate  I., 
Fig.  3,  and  Plate  III.,  Fig.  16).  The  vacant  sterigma  also  appeared 
<x>  be  quite  as  long  and  as  turgid  as  the  other  three  still  bearing 
spores.  The  basidium  did  not  seem  to  have  altered  in  volume. 
There  was  nothing  to  suggest  that  the  sterigma  had  opened  and 
discharged  a  mass  of  fluid  through  its  very  fine  neck.  The  end 
of  the  sterigma,  which  is  only  about  0'5  p  wide,  gave  the  im- 
pression of  being  closed.  Subsequently  two  further  discharges  of 
spores  were  observed.  There  was  an  interval  of  a  few  minutes 
between  two  successive  discharges.  Again,  each  sterigma,  im- 
mediately after  discharging  its  spore,  appeared  to  be  pointed  at 
its  end  and  devoid  of  any  terminal  drop  of  fluid.  Even  when 
three  spores  had  been  discharged,  I  was  unable  to  observe  any 
collapse  of  the  basidium.  All  four  sterigmata  appeared  to  be 
equally  turgid.  The  fourth  spore  remained  on  its  sterigma  for 
more  than  half-an-hour  after  the  discharge  of  the  third  and  was 
not  seen  to  disappear.  In  several  other  instances  one  or  two 

1  Massee,  in  his  Text-Book  of  Fungi  (London,  1906),  says  :  "  In  the  Hymeno- 
mycetes  the  mature  spore  is  cut  off  from  the  apex  of  its  sterigma  by  a  transverse 
wall.     The  sterigma  retains  its  parietal  protoplasm  after  the  spore  is  cut  off,  and 
its  elastic  wall  continues  to  stretch  as  the  tension  due  to  the  accumulation  of 
water  increases.     When  the  tension  reaches  a  certain   point,  the  wall   of   the 
sterigma  ruptures  in  a  circular  manner  just  below  the  septum  at  its  apex  ;  the 
elastic  wall  of  the  sterigma  instantly  contracts  and  forces  its  contained  water  to 
strike  the  apical  transverse  wall,  which  is  thus  thrown  off  along  with  the  spore 
seated  upon  it."     The  reader  is  unfortunately  left  in  doubt  as  to  the  authority 
upon  whom  reliance  has  been  placed  for  these  statements.     The  account  of  spore- 
discharge,  however,  is  similar  to  that  of  Brefeld  and  merits  the  same  criticisms. 

2  Chap.  XL 


150  RESEARCHES   ON  FUNGI 

spores  were  observed  to  be  discharged  from  the  sterigmata  in 
precisely  the  same  manner  as  that  described.  Similar  results  were 
obtained  with  Marasmius  oreades  and  Coprinus  comatus. 

The  small  size  of  the  basidia  and  the  difficulty  of  seeing  the 
narrow  neck  of  a  sterigma  where  it  is  joined  on  to  a  spore,  make 
it  extremely  difficult  to  observe  what  physical  change  takes  place 
at  the  end  of  the  sterigma  at  the  moment  of  spore-discharge. 
However,  after  consideration  of  all  the  observed  facts,  it  seems  to 
me  that  some  conclusion  as  to  the  mechanism  of  the  process 
may  be  drawn. 

The  first  theory  of  spore-discharge  which  we  may  consider 
is,  that  the  four  spores  are  shot  off  the  sterigmata  owing  to  the 
latter  breaking  at  their  ends  and  discharging  drops  of  fluid 
consisting  of  cell-sap  driven  out  of  the  basidium  by  the  contraction 
of  the  cell-wall.1  I  fail  to  find  any  facts  in  favour  of  this  con- 
ception. No  drops  could  be  detected  on  the  sterigmata  or  spores 
immediately  after  discharge.  The  disappearance  of  the  spores  did 
not  lead  to  any  observable  collapse  of  the  sterigmata  or  basidium. 
A  strong  adverse  argument  may  also  be  derived  from  the  fact 
that  the  spores  are  discharged  successively.  A  basidium  is  unicel- 
lular. If,  when  a  spore  was  discharged,  the  sterigma  broke  across 
and  a  drop  of  fluid  was  forced  out,  the  hydrostatic  pressure  in 
the  basidium  would  be  very  considerably  lessened.  There  would 
be  a  puncture  in  the  cell.  Under  such  conditions  it  seems  diffi- 
cult to  imagine  how  the  pressure  could  be  used  again  for  the 
successive  discharge  of  the  three  remaining  spores. 

It  seems  to  me  that  the  clue  to  explain  the  mechanism  of 
spore-discharge  can  be  obtained  from  comparative  studies  in  other 
groups  of  fungi.  In  the  Ascomycetes,  e.g.  Ascobolus,  the  spores 
are  evidently  driven  out  of  the  ascus  by  the  pressure  of  the  cell- 
wall  upon  the  cell-sap.  The  end  of  the  ascus  suddenly  breaks 
open,  the  ascus  collapses,  and  the  eight  spores  are  discharged 
simultaneously  along  with  the  cell-sap.  A  similar  mechanism  is 
to  be  found  for  Pilobolus  and  Empusa  Muscee.  There  is,  however, 

1  We  may  suppose  by  analogy  with  other  plant  cells  that  the  pressure  of  the 
cell-sap  upon  the  protoplasm  and  wall  of  the  basidium  is  due  to  the  process  of 
osmosis,  and  amounts  to  several  atmospheres. 


THE   MECHANISM   OF  SPORE-DISCHARGE         151 

another  way  in  which  the  hydrostatic  pressure  may  be  used  as  a 
driving  force.  This  is  illustrated  in  several  Entomophthorinese. 
In  Empusa  Grylli,  according  to  Nowakowski,1  the  wall  separating 
the  conidium  from  the  basidium  is  double.  There  is  a  tiny  colu- 
mella  projecting  into  the  former.  When  the  conidium  is  ripe, 
the  two  walls  separate  by  mutually  bulging  in  opposite  directions 
hi  response  to  hydrostatic  pressure  both  in  the  conidium  and  the 
basidium.  In  consequence  of  the  bulging  taking  place  very 
rapidly,  the  spore  is  shot  forwards  to  some  distance.  It  thus 
happens  that  the  basidium  is  not  punctured  in  discharging  its 
spore,  and  therefore  does  not  lose  any  cell-sap.  The  basidium 
merely  alters  its  shape.  It  becomes  slightly  enlarged  terminally, 
whilst  doubtless  contraction  takes  place  laterally.  Probably  during 
this  process  the  hydrostatic  pressure  of  the  cell-sap  upon  the  cell- 
wall  becomes  slightly  diminished.  We  have  a  process  which 
we  may  distinguish  as  the  jerking  discharge  as  opposed  to  the 
squirting  discharge  of  Empusa  Muscse  and  Ascobolus,  &c.2 

It  appears  to  me  very  probable  that  the  four  spores  are  dis- 
charged from  the  basidia  of  Hymenomycetes  by  a  jerking  process 
essentially  similar  to  that  just  described.  This  hypothesis  involves 
the  assumption  of  a  double  wall  separating  the  sterigma  and  spore, 
and  that  the  two  walls  mutually  bulge  so  as  to  press  against  one 
another  when  spore-discharge  takes  place.  That  such  a  double  wall 
in  each  sterigma  must  be  present  seems  to  be  proved  by  the  fact 
that  both  spore  and  sterigma  are  turgid  after  discharge.  The 
pointed  "  tail "  of  each  spore  and  the  pointed  end  of  the  sterig- 
mata  after  becoming  naked  are  facts  in  favour  of  the  idea  of  a 
mutual  bulging  of  the  two  walls  which  were  in  contact.  The 
hydrostatic  pressure  in  the  basidium  would  be  only  very  slightly 
diminished  as  each  spore  was  shot  off  and  would  be  available 

1  Quoted  from  Die  Pflanzen-familien  of  Engler  and   Prantl,  who   reproduce 
Nowakowski's  figures.     Teil  1,  Abteil  1,  Entomophthorineae,  p.  135. 

2  In  Bosidiobolus  ranarum  we  have  both  squirting  and  jerking  processes  in 
succession.     The  basidium  first  breaks  across,  and  the  outer  end  with  the  spore 
is  shot  away  by  the  squirting  process.     The  spore  is  then  shot  off  the  collapsed 
end  of  the  basidium  by  the  jerking  process.     The  spore-wall  at  the  place  of 
attachment   bulges   out   so  as  to   become  pointed.     In  Conidiobolus  utriculosus, 
apparently,  sometimes  the  squirting  process  is  used  and  sometimes  the  jerking. 
See  Engler  and  Prantl,  loc.  cit. 


152  RESEARCHES  ON  FUNGI 

for  the  discharge  of  them  all.  The  great  difficulty  in  verifying 
this  hypothesis  is  that  of  observing  what  happens  to  the  end  of 
the  sterigma  at  the  moment  of  spore-discharge.  However,  the 
following  facts  seem  to  be  distinctly  in  its  favour:  (1)  Successive 
discharge  of  the  four  spores,  (2)  absence  of  drops  on  the  end  of 
the  sterigmata  or  on  the  spores  immediately  after  discharge, 
(3)  apparent  closed  condition  of  the  sterigmata  after  ejecting 
their  spores,  and  (4)  non-collapse  of  the  sterigmata  and  basidium 
as  the  spores  disappear. 


CHAPTER    XIII 

THE  SPECIFIC  GRAVITY  OF  SPORES 

THE  measurements  described  in  this  and  the  following  chapter 
were  made  chiefly  with  the  object  of  testing  Stokes'  Law. 

In  order  to  determine  the  specific  gravity  of  spores,  the  heavy- 
fluid  method  was  employed.  Owing  to  the  minute  size  of  the  spores 
and' their  very  slow  rate  of  fall  even  in  water,  and  also  in  order 
to  reduce  convection  currents  to  the  least  possible  minimum,  it 
was  found  necessary  to  use  a  special  small  chamber  with  which 
to  carry  out  the  tests.  After  several  chambers  had  been  tried, 
the  most  suitable  one  proved  to  be  an  ordinary  Leitz-Wetzlar 
counting  apparatus,  such  as  is  used  for  estimating  the  number  of 
blood-corpuscles  in  drops  of  blood.  In  the  chamber  in  question 
the  distance  between  the  cover-glass  and  the  central  disc  is  only 
0*1  mm. 

The  mode  of  procedure  in  making  the  experiments  was  as 
follows :  A  fresh  fungus  was  obtained,  and  its  pileus  was  cut  off 
and  placed  on  a  piece  of  glass  or  paper,  where,  in  the  course  of 
a  few  minutes  or  hours,  a  spore-deposit  collected.  Some  drops 
of  the  solution  to  be  tested,  namely,  calcium  chloride  of  known 
specific  gravity,  were  then  poured  into  a  small  beaker.  Spore 
masses  were  scraped  up  from  the  spore-deposit  with  a  needle 
and  placed  in  the  solution.  This  was  then  stirred  vigorously,  so 
that  the  spores  became  well  separated  and  fairly  evenly  suspended 
in  it.  A  drop  of  the  fluid  containing  the  spores  was  next  placed 
in  the  Leitz-Wetzlar  apparatus  and  the  cover-glass  applied.  If 
the  spores  were  heavier  than  the  medium  in  which  they  were 
suspended,  they  gradually  sank  and  collected  on  the  bottom  of 
the  chamber.  If  they  were  lighter,  they  gradually  rose  and 
collected  beneath  the  cover-glass.  The  end-result  by  this  means 
could  usually  be  determined  in  a  few  minutes.  Convection  currents 


'54 


RESEARCHES   ON  FUNGI 


are  practically  reduced  to  nothing  in  the  chamber,  and  the  spores 
had  to  travel  at  most  upwards  or  downwards  only  a  distance  of 
0*1  mm.  By  focussing  and  watching  an  individual  spore  in  the 
fluid,  one  could  quickly  decide  whether  it  was  falling  or  rising. 

The  results  of  the  tests  for  Psalliota  campestris,  Coprinus 
plicatilis,  and  Amanitopsis  vaginata  are  given  in  the  following 
table,  where  R  indicates  that  the  spores  rose  in  the  fluid,  S  that 
they  sank,  and  RS  that  about  equal  numbers  rose  and  sank 
respectively : — 


.-!?         1* 

-S  >>G 

«o^g 

Specific  Gravity  Deterin 

inations. 

5-C-f 

??!! 

iPJ 

m 

3-z 

<s 

Sp.  gr.  of  CaCl2  solu- 

1-451-441-43 

1*41 

1-4 

1-3551-325 

1-305 

tions 

1-43 

1-21 

Coprinus  plicatilis 

B 

R 

R     S 

8 

S 

8 

8 

s  ! 

Sp.  gr.  of  CaCl2  solu- 

1-5  ] 

•34   1-32 

1-31 

1-305 

1-293 

l-271'OO 

tions 

1-31 

1-2 

Psalliota  campestris 

B 

| 

R 

R 

8 

8 

8 

S 

S 

Sp.  gr.  of  CaCl2  solu- 

j. 

1 

1-05      1-025      1-015 

1-01 

1-00 

tions 

1-02 

1-02 

Amanitopsis  vaginata 

R 

R 

R 

S(P) 

S 

S 

Sp.  gr.  of  cane-sugar 

1-03 

1-025 

1-02 

1-015 

i-oo 

solutions 

1-02 

1-02 

Amanitopsis  vaginata 

B 

R 

RS 

8 

S 

When  fresh  spores  are  placed  in  water  they  are  turgid  and 
fully  expanded,  and  present  the  same  appearance  as  they  have 
when  just  about  to  be  liberated  from  their  sterigmata.  However, 
in  solutions  of  calcium  chloride  the  spores  decrease  in  size.  In 
many  species  they  become  obviously  deformed.  The  spores  of 
Psalliota  campestris  in  a  calcium  chloride  solution  of  sp.  gr.  1'32 
are  indented  on  one  side,  and  the  spores  of  Coprinus  plicatilis  in 
a  solution  of  sp.  gr.  1-44  have  the  shortest  of  their  three  axes 
(cf.  Fig.  55,  A,  p.  162)  reduced  to  nearly  one-half.  The  decrease 


THE  SPECIFIC   GRAVITY  OF  SPORES  155 

in  volume,  if  such  there  is,  in  spores  of  Amanitopsis  vaginata  in 
a  solution  of  sp.  gr.  T02  is  so  small  as  not  to  be  observable.  The 
heavy-fluid  tests  only  give  us  the  apparent  specific  gravity  of  the 
spores.  There  seems  to  be  little  doubt  that  the  decrease  in  volume 
is  due  to  loss  of  water  which  passes  out  from  the  spores  by  osmosis 
in  accordance  with  well-known  laws.  Loss  of  water  from  the  spores 
must  of  necessity  increase  their  specific  gravity,  for  the  salts  and 
other  bodies  heavier  than  water  must  thereby  become  concentrated. 
We  can  conclude,  therefore,  that  the  apparent  specific  gravity  of 
the  spores  in  the  heavy  fluid  is  greater  than  the  specific  gravity 
of  the  spores  when  fully  expanded  in  water.  The  tests  with  the 
solutions  inform  us  that  the  true  specific  gravity  of  the  spores  is 
between  1  and  T43  for  Coprinus  plicatilis,  between  1  and  1'32 
for  Psalliota  campestris,  and  between  1  and  1-02  for  Amanitopsis 
vaginata.  In  the  last-named  species  the  result  obtained  with 
calcium  chloride  was  confirmed  by  means  of  a  solution  of  cane- 
sugar. 

By  determining  the  loss  of  volume  of  spores  of  Coprinus 
plicatilis  when  placed  in  a  calcium  chloride  solution  of  sp.  gr.  143, 
I  have  been  able  to  calculate  approximately  the  true  specific  gravity 
of  the  spores  in  water. 

With  the  aid  of  a  Poynting  Plate  Micrometer  the  spores  were 
measured  with  a  considerable  degree  of  accuracy.  Ten  long,  ten 
short,  and  ten  intermediate  axes  were  measured,  each  measurement 
being  made  on  a  different  spore.  The  average  size  of  the  spores 
was  thus  found  to  be — 

In  water 12-54  x  10-33  X  814 

In  CaCLj  solution,  sp.  gr.  1-43    .     11-76  x  10-18  x  4-5 

By  multiplying  the  three  axes  together  we  can  calculate  that  on 
the  average  for  each  spore — 
(volume  in  water)  :  (vol.  in  CaCl2  solution,  sp.gr.  1-43)  :  :  1054  :  538. 

We  may  conclude,  therefore,  that  when  a  spore  is  taken  from 
water  and  placed  in  the  calcium  chloride  solution,  its  volume  is 
approximately  halved. 

Now,  it  may  be  shown  that 

(l  —  x)vs  + xvs"  =  vs' 


156  RESEARCHES   ON  FUNGI 

where  x  represents  the  fractional  loss  of  volume  in  the  heavy  fluid, 
v  the  volume  of  the  spore  in  water,  s  the  apparent  specific  gravity 
of  the  spore  in  the  heavy  fluid,  s'  the  true  specific  gravity  of  the 
spore  in  water,  and  s"  the  specific  gravity  of  water  itself. 

Since  «  =  |,  s=l*43,  and  s"=l,  we  find  that  s'=l'215,  or  the 
true  specific  gravity  of  the  Coprinus  spores  in  water  is  approxi- 
mately 1-21. 

In  the  case  of  the  Mushroom,  owing  to  the  spores  becoming 
indented  on  one  side,  the  exact  loss  of  volume  of  the  spores  in  a 
calcium  chloride  solution  of  sp.  gr.  1-31  could  not  be  measured 
directly.  However,  it  was  estimated  by  inspection  as  being  from 
about  one-third  to  one-half  of  the  volume  in  water.  On  this 
assumption  we  may  calculate  from  the  equation  already  given  that 
the  specific  gravity  of  Mushroom  spores  is  approximately  1*2. 

'  The  Amanitopsis  spores  did  not  show  any  appreciable  con- 
traction in  the  calcium  chloride  solution  or  cane-sugar  solution 
of  sp.  gr.  1-02.  Since  we  have  already  found  that  the  real  specific 
gravity  of  the  spores  in  water  must  lie  between  1  and  1*02,  we 
may  take  it  that  the  real  specific  gravity  is  approximately  1*02. 
This  approximation  must  certainly  be  correct  to  within  1  per 
cent,  of  the  actual  specific  gravity. 

Another  method  for  estimating  the  specific  gravity  of  spores 
is  that  of  measuring  the  rates  of  fall  of  the  spores  in  air  and  in 
water.  The  data  so  obtained  are  then  used  in  the  following 
equation,  which  can  be  deduced  from  Stokes'  Law  which  must  be 
assumed  to  be  true : — 

v'^p-I^n 
v       p      M' 

where  v'  is  the  velocity  of  the  fall  of  spores  in  water,  v  the  velocity 
of  fall  in  air,  p,  the  viscosity  of  air,  p  the  viscosity  of  water,  and  p 
the  specific  gravity  of  spores. 

A  counting  apparatus,  with  a  chamber  1  cm.  square  above  and 
below  and  0*2  mm.  deep,  was  used  for  estimating  the  rate  of  fall 
of  the  spores  in  water.  The  chamber  was  filled  with  water  holding 
spores  in  suspension  and  covered  with  a  cover-glass.  A  microscope 
was  then  turned  into  the  horizontal  position  and  the  counting 
apparatus  clamped  down  to  the  now  vertically-placed  stage.  The 


THE   SPECIFIC   GRAVITY   OF  SPORES  157 

convection  currents  in  the  chamber,  although  not  entirely  absent, 
appeared  to  be  negligible.  In  the  case  of  Coprinus  plicatilis,  ten 
spores  were  carefully  timed  in  falling  through  a  field  of  1-6  mm. 
in  width.  On  the  average  each  spore  took  2  mins.  57  sees,  to 
fall  this  distance.  The  velocity  of  the  fall  of  the  spores  in  water 
was  thus  found  to  be  0*00090  cm.  per  second.  The  velocity  of 
fall  of  the  spores  in  air  was  found  by  finding  the  time  required 
for  them  to  fall  vertically  through  a  distance  of  4-55  mm.  from 
pieces  of  gills  placed  in  a  small  compressor  cell.1  The  speed  was 
found  to  be  0-429  cm.  per  second. 

Putting  v'  =  0-0009,  <y  =  0'429,  ^  =  l-8xlO-4,  and  /*'  =  l-2x  10"2, 
we  get  p,  the  specific  gravity  of  the  Coprinus  spores,  =  1-16. 

With  Mushroom  spores  it  was  found  that  v' —  0-00025  and 
v  =  0-13,  whence  p  =  1-15. 

Both  results  are  within  6  per  cent,  of  those  obtained  by  the 
other  method.  The  present  method  seems  to  me  to  be  less 
reliable  than  the  first  on  account  of  its  indirectness  and  the 
assumptions  involved.  Stokes'  Law  was  assumed  to  be  true :  the 
spores  were  not  spherical.  Possibly  the  errors  in  estimating  the 
rates  of  fall  of  the  spores  in  water  are  quite  appreciable.  Never- 
theless, the  result  may  be  correct  to  within  10  per  cent. 

If  we  take  the  results  given  by  the  heavy-fluid  method  to  be 
fairly  reliable,  we  may  conclude  that  the  specific  gravities  of  the 
spores  are  as  follows :  for  Coprinus  plicatilis  1*21,  for  Psalliota 
campestris  1*2,  and  for  Amanitopsis  vaginata  1*02.  The  spores 
of  the  last-named  species  are  much  lighter  than  those  of  the  other 
two.  This  is  probably  due  to  the  very  large  amount  of  oil  which 
the  spores  of  Amanitopsis  contain.  The  oil  is  certainly  a  very 
light  constituent  of  each  cell,  for,  when  a  spore  is  falling  in  water, 
the  large  oil  mass,  as  seen  with  the  horizontal  microscope,  occupies 
the  highest  position  possible.  On  account  of  the  spores  of 
Amanitopsis  vaginata  having  about  the  same  specific  gravity  as 
water,  it  was  not  found  possible  to  measure  the  rate  of  their  fall 
in  that  medium.  Their  motion  was  so  slow  that  even  minute 
convection  currents  proved  to  be  a  serious  source  of  error  in  making 
the  measurements. 

1   Vide  infra,  Chap.  XV. 


CHAPTER   XIV 

THE   SIZE   OF   SPORES— POYNTING'S   PLATE   MICROMETER 

EACH  species  produces  spores  of  a  definite  shape  and  size.  The 
spores  vary  in  size  about  a  mean,  doubtless  in  accordance  with  the 
now  well-known  laws  of  continuous  variation.  The  variations  as  a 
rule  are  within  fairly  restricted  limits,  so  that  fungus  spores,  when 
observed  with  a  microscope,  appear  to  resemble  one  another  very 
much  as  do  eggs  laid  by  a  fowl.  By  measuring  the  diameters  of 
twenty-five  spores  of  any  fruit-body,  one  can  obtain  an  average 
size  which  is  correct  to  within  a  very  small  percentage  of  the 
real  average  for  all  the  spores.  It  must  not  be  assumed,  however, 
that  all  the  individual  fruit-bodies  of  a  species  have  spores  of 
the  same  average  size.  Thus,  for  instance,  three  specimens  of 
Amanitopsis  vaginata,  obtained  from  the  same  wood  on  differ- 
ent days,  possessed  spores  with  an  average  diameter  of  ll'Go  /A, 
10-87  n,  and  10-19  //,  (Fig.  55,  B,  C,  D,  p.  162).  It  is  not  sur- 
prising that  the  spore  sizes  for  species  as  given  by  systematists 
often  disagree. 

For  the  purpose  of  measuring  spores  rapidly  and  accurately  I 
have  made  use  of  Poynting's  Plate  Micrometer,1  a  simple  and  exact 
piece  of  apparatus  which  should  come  into  general  use  in  all  inves- 
tigations where  it  is  necessary  to  measure  the  sizes  of  numerous 
small  bodies.  Since  it  seems  that  I  am  the  first  to  apply  the  Plate 

1  The  Plate  Micrometer  with  which  I  worked  was  Professor  Poynting's 
original  instrument.  My  thanks  are  due  to  him  for  kindly  permitting  me  to 
use  it  in  his  laboratory.  It  was  exhibited  at  an  Optical  Convention  held  in 
London  four  years  ago.  In  the  Proceedings  of  the  Optical  Convention,  No.  1,  Lon- 
don, 1905,  a  one-page  account  of  the  principle  of  the  micrometer  is  given,  but  this 
would  be  of  little  use  to  any  one  wishing  to  understand  how  the  measurements 
of  spore  dimensions  were  made.  Professor  Poynting  has  informed  me  that  he 
has  not  yet  published  an  adequate  description  of  the  Plate  Micrometer  as  applied 
to  the  microscope,  but  he  has  consented  to  my  attempting  to  show  how  the 

instrument  may  be  used  in  practice. 

.58 


THE   SIZE   OF  SPORES  159 

Micrometer  in  a  biological  research,  a  brief  description  of  it  here 
will  not  be  out  of  place. 

The  apparatus  is  provided  with  a  stand,  Plate  IV.,  Fig.  26,  st, 
attached  to  which  is  a  horizontal  arm,  a,  bearing  at  its  end  a  vertical 
scale,  sc.  The  scale  is  divided  into  fifty  parts,  with  the  zero  at  the 
top.  A  carefully  prepared  plate  of  glass,  6  mm.  thick,  p,  with 
parallel  upper  and  lower  faces,  is  attached  to  a  horizontal  rod,  rr 
which  is  fixed  to  the  stand  so  that  it  can  be  rotated  about  its  axis 
by  means  of  a  lever,  I.  The  end  of  the  lever  carries  a  small  frame- 
work in  which  is  placed  a  piece  of  glass.  On  the  latter  is  scratched 
a  fine  line  parallel  to  the  arm  of  the  lever.  The  line  serves  to 
indicate  the  position  of  the  lever  on  the  scale.  The  microscope 
is  provided  with  a  mechanical  stage.  It  also  has  a  slot,  si,  in 
the  tube  above  the  objective,  of  such  a  size  that  the  glass  plate  can 
readily  be  inserted  into  it.  The  eyepiece  contains  a  transverse  silk 
thread. 

When  the  apparatus  is  about  to  be  used,  the  glass  plate  is 
inserted  into  the  slot  so  that  it  becomes  entirely  enclosed  in  the 
microscope  tube,  which,  however,  it  does  not  touch.  The  eyepiece 
is  then  rotated  until  its  silk  thread  comes  to  be  parallel  to  the 
rod,  r,  bearing  the  glass  plate. 

The  scale,  sc,  is  calibrated  as  follows.  The  lever  is  first  raised 
until  the  line  in  the  terminal  framework  exactly  crosses  the  zero  of 
the  scale.  A  stage  micrometer  is  then  placed  on  the  microscope 
stage  so  that  its  dividing  lines  are  parallel  to  the  thread  in  the  eye- 
piece. By  using  the  mechanical  stage  one  of  the  micrometer  lines 
is  made  to  coincide  with  the  thread  of  the  eyepiece.  The  lever  is 
then  depressed.  This  causes  the  glass  plate  to  rotate  slightly.  As 
one  looks  down  the  microscope,  the  micrometer  line  appears  to  move 
parallel  to  itself  away  from  the  eyepiece  line.  By  depressing  the 
lever  far  enough,  one  can  make  a  second  stage  micrometer  line 
coincide  with  the  eyepiece  line.  Let  us  suppose  that  the  distance 
between  the  two  micrometer  lines  is  10  //,,  and  that  the  lever  has 
been  moved  downwards  through  twenty-six  divisions  on  the  vertical 

scale,  it  is  then  clear  that  each  scale  division  has  the  value  —  /*. 

13 

By  making  ten  measurements  between  ten  successive  divisions  of  the 


i6o 


RESEARCHES  ON  FUNGI 


stage  micrometer,  one  can  obtain  a  very  accurate  value  for  each 
division  of  the  plate  micrometer  scale. 

When  the  scale  has  been  calibrated  by  the  method  just  described, 
one  proceeds  to  measure  the  size  of  spores.  These  are  mounted  in 
water  on  a  glass  slide  and  covered  with  a  cover-glass  in  the  usual 
way.  The  lever  is  placed  at  zero.  One  then  finds  a  spore  with  the 
axis  to  be  measured  directed  at  right  angles  to  the  eyepiece  line.1 
Let  us  suppose  that  one  wishes  to  measure  the  long  axis.  With  the 
mechanical  stage  one  moves  the  spore  so  that  one  end  of  it  just 
touches  the  eyepiece  line  (Fig.  54).  One  then  depresses  the  lever 

from  the  zero  of  the  scale,  and  as  one 
does  so  the  spore  appears  to  move 
across  the  eyepiece  line  from  left  to 
right,  until  finally  it  comes  to  touch  it 
with  its  other  end.  At  this  point  one 
ceases  to  depress  the  lever  and  reads 
off  the  number  of  divisions  on  the  scale 
through  which  it  has  been  moved.  By 
measuring  twenty-five  spores  in  this 

"V.  °°»  ^  °b^»  a  ™T  good  aver- 
age  on  the  scale  for  the  dimensions 
required.  Since  the  actual  value  or  a 

^     micrometer    gcale    diyision    hag 

previously  been  found  by  calibration,  the  dimensions  of  the  spores 
can  readily  be  calculated. 

The  advantages  of  the  apparatus  are  :  (1)  Its  optical  soundness 
—  each  division  on  the  vertical  scale  has  the  same  value;  (2)  the 
apparatus  is  entirely  detached  from  the  microscope,  so  that,  when 
the  lever  is  moved,  the  microscope  cannot  be  shaken  in  any  way  ; 
(3)  the  accuracy  with  which  the  scale  can  be  calibrated  ;  (4)  its 
simplicity  ;  (5)  the  speed  and  ease  with  which  large  numbers  of 
observations  can  be  made  with  it. 

The  range  of  variation  in  the  sizes  of  spores  may  be  gathered 

1  With  the  addition  of  a  rotating  stage  one  could  place  any  spore  with  its  axis 
in  the  desired  direction.  My  microscope,  unfortunately,  was  without  this  refine- 
ment. There  is,  however,  very  little  difficulty  in  finding  as  many  spores  as  one 
requires  with  their  axes  in  the  right  direction. 


r  b,      ^ySTSS.*;  S£ 
Micrometer.     By  depressing  the 

lever  the  spore  appears  to  move 

across  the  eye-piece  line  EE  from 

position  A  to  position  B. 


THE   SIZE   OF  SPORES  161 

from  the  following  example,  which  gives  the  plate  micrometer  scale 
figures  obtained  for  the  diameters  of  100  fresh  spores  of  Amanitopsis 
vaginata  (Specimen  III.)  measured  in  water : — 


41-0 

43-0 

40-1 

45-5 

40-7 

41-3 

40-8 

47-5 

38-5 

42-7 

39-5 

41-5 

39-5 

3(5-0 

43-6 

43-0 

38-6 

40-2 

43-1 

39-0 

40-0 

36'5 

43-4 

42-0 

47-0 

42-7 

37-4 

38-0 

400 

41-8 

45-0 

38-0 

38-0 

39'5 

40-7 

36'8 

44-7 

36-0 

45-0 

43-0 

40-2 

455 

39-2 

40-8 

43-5 

42-5 

39-8 

43-4 

39-8 

39-4 

42-8 

41-5 

39-0 

44-0 

42-3 

39-7 

39-8 

48-0 

41-4 

46-2 

35-6 

38-0 

38-7 

41-0 

43-4 

38-2 

43-0 

39-5 

40-4 

36-1 

40-8 

39-4 

40-0 

41-0 

40-5 

36-1 

40-0 

41-0 

42-1 

41-3 

410 

38-4 

42-0 

43-6 

40-7 

39-2 

40-5 

38-0 

38-1 

41'0 

41-6 

42-5 

41-4 

40-5 

40-8 

45-4 

43'9 

40-8 

39-4 

36-6 

407-5     404-3     401'5     413'9     422'6     404'9     408'5     412'4     407'8     407-1 

,The  average  scale  measurement  for  the  spore  diameters  of  100 
spores  was  found  to  be  40*905.  The  calibration  figures  for  ten  suc- 
cessive distances  of  10  ^  each  on  a  stage  micrometer  were  as 
follows  : !  34-5,  36-1,  35-0,  351,  36-0,  34-5,  34-5,  35*4,  36'0, 34-5,  whence 
it  was  calculated  that  yn  =  3'51  plate  micrometer  scale  divisions.  The 

average  diameter  of  100  spores,  therefore,  =  =11-65  M. 

3"o  1 

The  Table  on  page  162  gives  some  of  the  results  of  measurements 
with  the  Poynting  Plate  Micrometer.  Each  measurement  given 
is  the  average  of  25  or  50  measurements  of  25  or  50  spores  respec- 
tively. The  last  column  gives  the  value  «/l°ng  axis  x  short  axis. 

Illustrations  of  all  the  spores  in  the  Table  are  given  in 
Fig.  55. 

From  the  Table  the  general  range  in  size  of  the  spores  of 
Agaricineoe  may  be  gathered.2  The  very  large  spores  of  Coprinus 
plicatilis  are  about  twenty-two  times  the  volume  of  the  very  small 
spores  of  Collybia  dryophila.  In  all  cases,  however,  and  this 
may  be  stated  quite  generally  for  the  Hymenomycetes,  the  spores 
are  so  small  that  they  must  fall  in  the  manner  indicated  by  Stokes' 
Law,  i.e.  almost  immediately  after  liberation  (within  a  very  small 

1  The  differences  between  these  readings  are  due  to  errors  in  the  construction 
of  the  stage  micrometer,  and  not  to  any  want  of  delicacy  on  the  part  of  the  Plate 
Micrometer. 

2  The  largest  spores  of  any  known  Agaric  are  those  of  the  exceptional  Coprimts 
gigasporus,  which  measure  28-30  x  14-16  ^.    G.  Massee,  "A  Revision  of  the  Genus 
Coprinus,"  Ann.  of  Bot.,  vol.  10,  p.  123. 

L 


1 62  RESEARCHES   ON   FUNGI 

fraction  of  a  single  second)  they  must  fall  without  acceleration  at 
a   uniform  speed.     The  size  of  the  spores  is   also  such  that  this 


Species. 

Lon?  Axis 
in  p. 

Short  Axis 
in  ju. 

Geometrical 
Mean  of  the 
Two  Axes 
inM. 

Collybia  dryophila 

5-44 

323 

4-2 

Pluteus  cervinus  . 

5-95 

4-57 

5-2 

Paxillus  involutus 

7-48 

4-88 

6-0 

Psalliota  campestris  : 

Grown  on  a  bed,  I.  . 

7-17 

5-41 

6-25 

»        ,.         »    II- 

7-26 

5-35 

6-25 

,!     „     »  ni.     . 

7-32 

5-64 

6-4 

From  a  field,         IV. 

9-7 

5-80 

7-4 

Marasmius  oreades 

9-5 

5-6 

7-4 

Boletus  badius     . 

12-8 

4-29 

7-4 

Amanita  rubescens 

9-38 

6-53 

7-8 

Galera  tenera 

10-47 

606 

7-96 

Russula  emetica  . 

8-82 

7-50 

8-2 

Polyporus  squamosus  . 
Coprinus  comatus 
Amanitopsis  vaginata,  I. 

14-6 
12-55 

10- 

5-13 

7-48 
19 

8-7 
9-8 
10-19 

II-    • 

10-87 

1087 

III.  . 

11-65 

11-65 

Coprinus  plicatilis 

12-9      10-7      7-9 

11-8 

uniform  speed  is  only  about  0-5-6  mm.  per  second.      The  spores, 
therefore,   are   so   tiny   that   even   the    slightest    air-currents    can 

A  BCDEFCH 

*••••••!• 


M        N 


•tit 


0  R 

t     I 


o          lou      a.ou, 

FIG.  55.— The  average  spores  of  individual  fruit-bodies  of  various  species  of 
Hyruenomycetes.  A,  Coprinus  plicatilis;  B,  C.  and  D,  three  individuals  of 
Amanitopsis  vaginata;  E,  Coprinus  comatus ;  F,  Russula  emetica;  G,  Poly- 
porus squamosus  ;  H,  Galera  tenera ;  I,  Amanita  rubescens;  J,  Boletus  badius; 
K,  Marasmius  oreades;  L,  M,  N,  and  0,  four  individuals  of  Psalliota  campestris; 
P,  Paxillus  involutus ;  Q,  f-luteus  ceroinus ;  R,  Collybia  dryophila. 

carry  them  long  distances  away  from  the  fruit-bodies  upon  which 
they  have  been  developed. 


THE   SIZE   OF   SPORES  163 

The  difference  between  the  average  size  of  the  spores  for 
individual  fruit-bodies  is  indicated  by  the  results  obtained  for 
Psalliotct  campestris  and  Anumitopsis  vaginata.  The  field  Mush- 
room probably  belonged  to  a  variety  distinct  from  that  of  the 
cultivated  ones.  It  was  characterised  not  only  by  relatively  iriuch 
longer  spores  but  also  by  much  deeper  gills. 

The  average  diameter  of  the  spores  for  Specimen  III.  of 
Amanitopsis  vaginata  was  14'3  per  cent,  larger  than  the  average 
size  for  Specimen  I.  It  is  clear  from  this  instance  that  fruit- 
bodies  of  the  same  species  may  have  considerable  individual 
variability  in  regard  to  the  average  size  of  their  spores. 


CHAPTER   XV 

THE  RATE   OF   FALL  OF   SPORES  AND   STOKES'  LAW— APPENDIX 

So  long  ago  as  1851  Stokes1  published  a  paper  called  "On  the 
Effect  of  Internal  Friction  of  Fluids  on  the  Motion  of  Pendulums." 
In  the  course  of  a  mathematical  treatment  of  his  data,  he  deduced 
an  equation  expressing  the  relations  between  the  density  of  a 
falling  microscopic  sphere,  the  size  of  the  sphere,  the  velocity 
of  its  fall,  the  density  of  the  fluid  through  which  it  may  fall,  and 
the  viscosity  of  the  fluid.  The  equation  represents  what  is  known 
as  Stokes'  Law : 2 


where  V  =  the  terminaljvelocity, 

p  =  the  density  of  the  falling  sphere, 
<r=the  density  of  the  medium, 
g  =  the  acceleration  due  to  gravity, 
a  =  the  radius  of  the  falling  sphere, 
p.  =  the  viscosity  of  the  medium. 

For  more  than  forty  years  this  equation  remained  untested 
for  the  fall  of  small  particles  in  air  and  other  gases.  This,  no 
doubt,  was  due  to  the  technical  difficulties  of  procuring  microscopic 
spheres  of  known  density  and  size,  and  of  dropping  them  through 
gaseous  media  in  such  a  manner  that  their  rate  of  fall  could  be 
measured.  The  verification  of  Stokes'  Law  by  means  of  such 
experiments  has  recently  become  of  some  importance  owing  to 
the  necessity  of  assuming  it  in  investigations  upon  the  electronic 
charge  as  made  by  J.  J.  Thomson3  with  the  cloud  method. 

The  only  evidence  hitherto  4  adduced  to  show  that  Stokes'  Law 

1  G.  Stokes,  Camb.  Phil.  Trans.,  vol.  ix.,  Part  II.,  p.  8. 

•  Cf.  the  Appendix  to  Chap.  XVII. 

3  J.  J.  Thomson,  Phil.  Mag.,  December  1898;  December  1899. 

*  This  was  written  in  1907.      Since  then  Zeleny  and  M'Keehan  have  recorded 
experiments  with  lycopodium  powder.     Vide  the  Appendix. 

164 


THE  RATE  OF  FALL  OF  SPORES 


165 


holds  for  the  fall  of  small  spheres  in  air  appears  to  be  that  obtained 
by  J.  J.  Thomson,  whose  value  of  the  electronic  charge,  obtained 
by  Wilson's1  cloud  method  involving  the  assumption  of  Stokes' 
Law,  was  found  to  agree  with  the  generally  accepted  value  of  the 
electronic  charge  as  calculated  by  application  of  the  kinetic  theory 


FiG.  56. — Amanitopsis  vayinata.  Kelations  of  the  spores  to  the  fruit-body.  A, 
transverse  section  through  two  gills  showing  the  hymenium,  A,  from  which 
basidia  are  projecting.  The  arrows  indicate  the  paths  of  spores  which,  after 
discharge  from  their  basidia,  have  fallen  in  still  air.  Magnification,  15.  B, 
vertical  section  through  the  hymenium  and  subhymenium.  p,  paraphyses  : 
a-e,  basidia ;  a,  with  rudimentary  spores ;  6,  with  ripe  spores  ;  c,  with  two 
spores  discharged  ;  d,  with  three  spores  discharged  ;  c,  with  all  the  spores 
discharged  :  «,  the  subhymenium.  Magnification,  370.  C,  isolated  basidium 
with  two  spores  discharged  showing  mode  of  attachment  of  spores  to  their 
sterigmata.  Magnification,  1110.  D,  discharged  spore.  Magnification, 
1110.  E,  basidium  with  rudimentary  spores.  Magnification,  1110. 

of  gases.     This  verification  of  the  applicability  of  Stokes'  Law  is, 
of  course,  very  indirect. 

It  seemed  to  me  of  interest  to  attempt  to  determine  experi- 
mentally whether  the  spores  of  Hymenomycetes  fall  in  accordance 
with  Stokes'  Law.     It  was  hoped  that,  by  making  three  separate 
measurements  of  the  specific  gravity,  size,  and  velocity  of  fall  of 
1  C.  T.  R.  Wilson,  Phil.  Trans.,  1897. 


166  RESEARCHES   ON  FUNGI 

the  spores,  one  might  obtain  a  direct  test.  It  was  also  thought 
that  an  actual  determination  of  the  rate  of  fall  of  spores  would 
throw  light  upon  the  distribution  of  bacteria,  spores,  and  other 
organic  particles  in  air,  and  also  help  to  explain  fruit-body  structure. 
A  considerable  amount  of  preliminary  experimentation  was 
undertaken,  during  which  observations  were  made  upon  the  rates 
of  fall  of  spores  of  various  shapes  and  sizes  in  still  air.  The  spores 
of  Amanitopsis  vaginata  were  then  chosen  as  material  for  a  critical 
test  of  Stokes'  Law  for  the  following  reasons  :  (1)  They  are  spherical 
except  for  a  tiny  "  tail,"  and  smooth-coated  (Fig.  55,  A,  B,  and  C, 
p.  162).  (2)  They  are  comparatively  large,  so  that  one  can  measure 
their  diameters,  which  are  about  10  /*  wide,  very 
accurately  with  the  Poynting  Plate  Micrometer. 
(3)  Their  density  is  almost  that  of  water,  and 
can  be  measured  within  1  per  cent,  of  ac- 
curacy.1 (4)  They  could  easily  be  procured,  for 
the  fruit-bodies  of  Amanitopsis  vaginata  came 
up  in  sufficient  abundance  in  Sutton  Park, 
which  was  not  many  miles  from  the  laboratory. 
FIG.  57.—  Diagram  to  Fresh  fruit-bodies  (Plate  IV.,  Fig.  30)  could  be 
obtained  throughout  August  and  September, 


placed  in  the  com-     during  which  time  the  critical  experiments  were 

pressor  cell.  The  gills 

are  directed  vertically    made.     The  relations  of  the  spores  to  the  fruit- 

body  are  shown  in  Fig.  56. 

An  experiment  to  measure  the  rate  of  fall  of  Amanitopsis  spores 
was  carried  out  in  the  following  manner.  A  fresh  fruit-body  was 
obtained  from  the  woods  and  used  within  a  few  hours  of  being 
gathered.  Due  care  was  taken  in  carrying  the  fruit-bodies  to  the 
laboratory,  upon  reaching  which  they  were  immediately  placed 
upright  in  a  wet  sand-bath  and  covered  over  Avith  a  large  bell-jar. 

A  small  piece  of  the  pileus,  including  portions  of  three  gills,  was 
then  dissected  out  (Fig.  57)  and  placed  in  a  compressor  cell  in  the 
position  shown  in  Fig.  58,  p.  To  prevent  the  falling  spores  from 
drying,  two  soaked  pieces  of  blotting-paper  or  cotton-wool,  6,  and  a  few 
drops  of  water,  w,  were  then  added.  Upon  the  cap  being  adjusted,  the 
piece  of  fungus  became  fixed  by  slight  compression  and  hermetically 
1  Vide  Chap.  XIII. 


THE  RATE  OF  FALL  OF  SPORES 


167 


FIG. 


sealed  in  the  disc-shaped  chamber  of  which  the  base  and  top  con- 
sisted of  glass.  The  compressor  cell  was  then  placed  in  the  vertical 
position  (i.e.  with  the  glass  plates  vertical)  and  clamped  by  one  end 
to  a  stand.  By  this  means  it  was  possible  to  cause  the  gills  to  look 
vertically  downwards  in  the  natural  manner.  Thus  enclosed  in  the 
chamber,  the  gills  continued  to  rain  down  spores  for  some  hours. 

In  order  to  observe  the 
falling  spores,  a  special  micro- 
scope on  a  stand  of  simple 
construction l  was  employed. 
The  microscope  tube  was  placed 
in  the  horizontal  position 
(Plate  IV.,  Fig.  29),  and  could 
be  screwed  upwards  and  down- 
wards by  means  of  a  rackwork 
on  the  stand.  The  amount  of 
rise  or  fall  could  be  read  off 
on  a  vertical  scale  to  which 
a  vernier  was  attached.  The 
microscope  tube  was  arranged 
at  such  a  height  and  at  such  a 
distance  from  the  chamber  as 
to  focus  a  field  (shown  by  the 
dotted  ring  in  Fig.  58)  immedi- 
ately below  the  gills  where  the 
spores  were  falling.  To  illu- 
minate the  microscope,  diffuse 
daylight,  obtained  from  the 
glass  roof,  was  reflected  into 
the  tube  by  means  of  a  plane  mirror  (Plate  IV.,  Fig.  29).  The 
observations  were  made  in  a  basement  room  where  the  temperature 
was  very  constant  for  considerable  intervals  of  time. 

The  horizontal  microscope  was  provided  with  a  Ramsden  eye- 
piece.    Three  fine  silk  threads  were  attached  to  it  so  as  to  cross  the 
field  of  view.     The  distance  between  the  extreme  threads,  as  seen  in 
the  field  of  view  when  the  microscope  was  focussed,  was  4'55  mm. 
1  Made  by  Pye  &  Co. 


58.  —  The  compressor  cell  used  for 
measuring  the  rate  of  fall  of  spores.  A 
section  of  the  cell  is  shown  above :  the 
chamber  c  can  be  varied  in  size  by  rais- 
ing or  pressing  down  the  cap.  g,  glass. 
Below  is  shown  the  cell  when  in  use.  ;<, 
a  piece  of  pileus  with  gills  looking  down- 
wards (c/.  Fig.  57);  6,  b,  wet  blotting- 
paper  or  cotton-wool;  w,  a  free  drop  of 
water.  The  dotted  circle  shows  the  field 
of  view  of  the  horizontal  microscope  when 
focussed  just  beneath  the  gills.  The 
three  arrows  show  the  courses  of  three 
spores  falling  from  between  the  gills  and 
crossing  the  field.  The  horizontal  lines 
in  the  latter  are  produced  by  three  silk 
threads  in  the  Ramsden  eye- piece.  Actual 
size. 


i68  RESEARCHES   ON  FUNGI 

(Fig.  59),  while  above  and  below  them  there  was  a  further  space 
of  0*5  mm.  The  magnification,  namely,  about  25  diameters,  was 
obtained  by  using  a  No.  1  Leitz  objective  and  extending  the  draw- 
tube. 

On  viewing  a  field  just  below  the  gills,  spores  can  be  seen  as 
distinct  but  only  just  visible,  very  minute,  dark  objects,  steadily 
crossing  the  field  in  a  vertical  direction,  apparently  from  below 
upwards.  Every  spore  so  falling  is  not  in  focus,  but,  when  the  fungus 
material  is  in  good  condition,  spores  in  focus  come  into  view  at  least 

^, i  every    five    seconds.      Often    one    can    see 

three,  four,  or  five  spores  in  focus  at   the 
Is     same  time. 

The    spores    fall    vertically    downwards 
(apparently  upwards).     In  the  small  cham- 
ber  employed,  convection  currents  are  re- 
duced   to    a    minimum    and    produce    no 
FIG.  59.— The  field  of  the 
horizontal     microscope,     apparent  disturbing  effects  on  one  s  obser- 

apart  ^ThT^ppCT^nd     vations.      Doubtless,   there   are    very    slow 
lower  horizontal  threads     air.currents  in    the   chamber,   but    I   have 

in    the    eye-piece   when 

seen  in  the  field  of  view     no  reason  to  suppose  in  my  critical  experi- 

was  4-55  mm.  .          . 

ments  with  the  large  spores  of  Amamtopsis 

that  they  produced  an  error  in  the  record  of  speeds  of  2  per  cent. 
Even  with  the  small  spores  of  Collybia  dryophila,  which  often 
take  eleven  seconds  to  cross  the  field,  the  direction  of  the  paths 
of  fall  is  vertical  and  there  is  practically  no  swerving  from  the 
course. 

The  records  of  the  velocity  of  fall  of  the  spores  whilst  crossing 
the  field  of  the  horizontal  microscope  were  made  with  the  aid  of 
a  large  drum,  which  was  driven  by  electricity  and  provided 
with  a  delicate  regulator  (Plate  IV.,  Fig.  29).  A  recording 
fountain-pen  produced  a  continuous  spiral  line  upon  the  paper 
as  the  drum  rotated.  To  the  pen  was  attached  an  electric 
tapping  key,  which  could  be  placed  in  a  convenient  situation 
near  the  microscope.  When  the  knob  of  the  contact  apparatus 
was  depressed,  the  pen  immediately  deviated  from  its  course  upon 
the  paper. 

When  the  apparatus  was  ready,  the  drum  was  set  going  and  the 


THE  RATE  OF  FALL  OF  SPORES 


[69 


fall  of  spores  watched  through  the  microscope.     As  soon  as  a  spore 
clearly  came  into  view  at  the  bottom  of  the  field,  it  was  followed 


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RESEARCHES  ON  FUNGI 


second1   and  third  contacts  were   made   as  the  spore  crossed  the 

second  and  the  third  lines 
respectively.  Thus  for 
the  fall  of  each  spore  the 
pen  deviated  three  times 
from  its  normal  path  on 
the  paper  of  the  drum 
(Figs.  60  and  61).  The 
fall  of  about  100  spores 
was  recorded  in  this  way 
as  rapidly  as  possible,  the 
entire  record  usually  be- 
ing completed  in  less  than 
fifteen  minutes.  A  time 
record  of  ten  seconds  was 
always  made  on  the  drum 
before  and  after  each 
series  of  observations  by 
means  of  a  chronometer 
ticking  half-seconds.  The 
drum  kept  up  a  very  con- 
stant peripheral  velocity, 
which  was  usually  T16 
cm.  per  second.  When  the 
records  had  been  made, 
they  were  measured  off 
on  the  drum  by  means  of 
a  steel  tape,  added  up,  and 
the  average  taken.  By 
measuring  the  distance 
run  by  the  drum  in  ten  seconds,  the  speed  of  the  drum  could  be 
determined.  The  average  length  of  time  represented  by  the  average 

1  There  was  no  absolute  necessity  to  record  the  passing  of  the  middle  line  by 
a  spore,  but  it  was  found  convenient  to  do  so  for  the  purpose  of  distinguishing 
the  individual  spore-records  from  one  another  on  the  drum.  Every  effort  was 
made  to  make  the  first  and  third  contacts  precisely  at  the  times  the  upper  and 
lower  lines  were  being  crossed ;  but  the  second  contact,  being  of  quite  secondary 
importance,  was  naturally  not  always  recorded  so  accurately.  The  middle  line 
was  2'22  mm.  from  the  upper  line  and  2'33  mm.  from  the  lower  line. 


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THE  RATE  OF  FALL  OF  SPORES 


171 


record  of  the  spores  on  the  drum  could  then  be  calculated.  Since 
this  average  time  was  that  required  for  the  spores  to  fall  through 
a  distance  of  4'55  mm.,  the  average  velocity  of  fall  of  the  spores 
could  be  calculated. 

The  following  figures  give  the  drum  records  of  200  spores  of 
Amanitopsis  vaginata.1  The  first  series  of  100  took  about  twelve 
minutes  to  record.  After  an  interval  of  forty  minutes,  the  second 
series  of  100  was  made.  The  drum  records,  measured  on  the  drum 
by  means  of  a  steel  tape,  are  given  in  centimetres. 


SERIES  I.                                                     SERIES  II. 

0-85         0-80        0-85         O95         0'88 

0-70         1-05         0-85         0-74         0'85 

0'9o         0-86         0-87         0-97         0'89 

1-03         0-91         0-75         0-68         0'84 

0-95         0-89         0-89         0'93         0-65 

0-88         0-88         0-75         0-75         0-85 

0-95         0-90         0'78         0'91         0'75 

0-96        0-76        0-99        076        0'80 

0-84         0-80         0-88         0'90         0'89 

0-80         0-81         1-00         0-80         0-74 

0'71         0-88         0-82         0-95         0'90 

0-80         1-05         0-75         0-84         0'76 

0-85         0-95         0-85         0'75         0'82 

1-01         0-94        0-99        0-86        0'77 

0-92         0-89         0-86         0'99         0'78 

0-95        0-94        0-75        0'87        0-76 

0-84         0-85         0-94         0'82         0'84 

0-90        0-75        0-79        0'79        0-82 

0-96         0-89         0-90         0-93         O90 

0-99        0-85        0-83        0'80        0'94 

0-84         0-80         0-92         0'89         O94 

0-93         0-85         0-68         0'92         0'88 

0-80         0-94         0-94         0'99         O64 

0-92        0-80        0-92        0-91         0'89 

0-73         0-94         0-89         0'78         0'75 

0-95         0-84         0-89         0'88         0'92 

0-82         0-99       '0-85         0'81         0'72 

1-08         0-90         0-85         0-92         0'96 

0-84         0-89         0-82         0'85         0'74 

0'93         0-65         0-85         0'80         0'94 

0-84         0-89         0-85         0'84         O92 

0-96         0-85         0-75         0'85         1'04 

0-97         0-93         I'OO        0-79        0'91 

1-04         0-91         0-81         0-94         0'89 

0-90         0-89         0-97         0-85         0'85 

0-99        0-95         0-90        0'91         0'95 

1-00        0-90        0-85        0-74        0'60 

0-91         082         0-90         0-94         0'88 

0-77        0-87         0-95        0'90        O95 

1-00        0-90        0-90        0-90        0-81 

17-33       17-75       17-68       17-54       16-32 

18-73       17-41       16-90       16-86       17'29 

Sum  of  totals     .     .     17'33 

Sum  of  totals     .     .     18'73 

17-75 

17-41 

17-68 

16-90 

17-54 

16-86 

16-32 

17-09 

Grand  total  .     .     .     86'62  cm. 

Grand  total  .     .     .     87*19  cm. 

Average  distance  on  drum  in  Series  I. 

Average  distance  on  drum  in  Series 

=  0-8662  cm. 

II.  =  0-8719  cm. 

Average  speed  of  drum  =  l-16  cm.  per 

Average  speed  of  drum  =  1  -16  cm.  per 

second. 

second. 

Hence  average  time  of  fall  of  each 

Hence  average  time  of  fall  of  each 

spore  in  falling  through  a  field  of  4'55 

spore  in  falling  through  a  field  of  4'55 

mm.  =  0-747  seconds. 

mm.  =  0-752  seconds. 

4'55 
Hence  average  velocity  of  fall  = 

Hence  average  velocity  of  fall=  -^..^ 

U*  <  DZ 

=  6'09  mm.  per  second. 

=  6*05  mm.  per  second. 

Hence  average  velocity  for  both  Series  together  =  6-07  mm.  per  second. 


Specimen  I.  in  Chap.  XIV. 


172  RESEARCHES   ON  FUNGI 

The  Table  on  the  next  page  gives  a  summary  of  the  data  obtained 
for  testing  Stokes'  Law  with  falling  spores  of  Amanitopsis  vaginata. 
The  velocities  given  are  the  average  velocities  of  200  spores  in 
Specimen  I.,  of  100  in  Specimen  II.,  and  of  50  in  Specimen  III.  The 
densities  are  certainly  correct  to  within  1  per  cent.1  The  diameters 
are  the  average  diameters  for  at  least  50  spores,  these  being  spherical. 
The  measurements  were  made  with  a  Poynting  Plate  Micrometer  in 
the  manner  already  described.  The  spores  of  Specimen  I.  were 
those  collected  at  the  bottom  of  the  compressor  cell  whilst  observa- 
tions on  the  fall  of  some  of  them  were  being  made.  The  spores  of 
Specimen  II.  were  obtained  from  another  part  of  the  fruit-body  from 
which  the  piece  had  been  dissected  out  for  velocity  observations  in 
the  compressor  cell.  The  spores  of  Specimen  III.2  were  those  col- 
lected from  the  piece  of  fungus  used  for  the  velocity  records,  but 
collected  from  it  immediately  after  these  had  been  taken.  It  is 
clear,  therefore,  that  I  was  unable  to  measure  the  diameters  of 
exactly  those  spores  for  which  the  velocity  of  fall  had  been  recorded. 
This  is  a  defect  in  my  method.  However,  the  defect  seems  to  me 
of  little  importance,  for  it  was  found  that  any  50  spores,  taken  at 
random  from  any  part  of  a  single  fruit-body,  have  the  same  average 
size.  In  order  to  obtain  the  average  size  of  the  spores  of  which 
the  velocity  had  been  recorded,  it  was  therefore  only  necessary  to 
measure  the  average  size  of  any  50  spores  obtained  from  the  fruit- 
body. 

In  making  calculations  with  Stokes'  equation,  the  viscosity  of 
air3  was  assumed  to  be  1'8  x  10~4  and  its  density  negligible  compared 
with  that  of  a  spore.  The  value  of  g  was  taken  as  981. 

From  the  Table  it  is  clear  that  the  figures  obtained  by 
observation  for  the  rate  of  fall  of  the  spores  are  of  the  same 
order  of  magnitude  as  those  demanded  by  Stokes'  Law.  How- 
ever, the  Law  is  not  confirmed  in  detail,  for  as  an  average  for  the 
three  cases  it  was  found  that  the  actual  velocity  of  fall  of  the 
spores  was  46  per  cent,  greater  than  the  calculated. 

1  Vide  Chap.  XIII. 

2  For  actual  measurements,  vide  Chap.  XIV. 

8  1-8  x  ID'*  is  the  value  usually  taken  for  dry  air  at  room  temperatures.     The 
effect  of  moisture  is  to  very  slightly  reduce  the  viscosity. 


THE  RATE  OF  FALL  OF  SPORES 

A manitopsis  Vaginata 


173 


Chamber,  containing  soaked  blotting-paper  or  cotton-wool  and  free  water  below, 
closed  for  half-an-hour  before  observations  for  velocity  were  taken.  Field  of 
microscope  close  under  gills. 


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Specimen  I.  1'02  11  "65.  6  "07 
Specimen  II.  1-02  10'19  !  4'85 
Specim  en  III.  I  1  '02  1 10  -87  j  5  •  1 1 


4'14 
3-21 
3-64 


47 
51 
40 


14-0 

12-52 

12-9 


-16-8 
-18-6 
-15-0 


It  is  difficult  to  explain  why  the  observed  velocities  of  fall 
should  be  nearly  50  per  cent,  greater  than  that  demanded  by 
Stokes'  Law.  However,  perhaps  the  explanation  has  some  con- 
nection with  the  fact  (to  be  discussed  more  fully  in  the  next 
chapter)  that,  even  in  an  apparently  saturated  chamber,  the 
spores  in  falling  even  such  a  small  distance  as  5  mm.  lose  a 
certain  amount  of  water.  It  was  found  that  after  leaving  the 
gills,  the  rate  of  fall  of  the  spores  slightly  decreases.  Further 
experiment  showed  that  this  was  due  to  the  contraction  in  the 
volume  of  the  spores  consequent  on  drying  up.1  It  has  been 
suggested  to  me  by  Professor  Poynting,  that  the  loss  of  water 
by  a  spore  during  its  fall  might  lead  to  an  evaporation  pressure 
of  such  a  kind  that  the  spore  would  be  forced  more  quickly  down- 
wards than  would  be  the  case  if  no  loss  of  water  were  taking 
place.  Owing  to  the  impossibility  of  employing  perfectly  dry 
spores  in  my  experiments,  there  seems  to  be  no  way  at  present 
to  test  this  hypothesis. 

That  the  speed  of  fall  on  the  average  was  found  to  be  46  per 
cent,  greater  than  that  given  by  Stokes'  Law  may  possibly  be 
accounted  for  by  surface  slip.  With  very  minute  particles  Stokes 

1  Vide  infra,  Chap.  XVI. 


174  RESEARCHES   ON   FUNGI 

has  calculated  that  the  maximum  effect  of  slip  is  to  increase  the 
terminal  velocity  by  50  per  cent.  Therefore,  if  we  assume  that 
the  slip  actually  takes  place,  the  discrepancy  between  observation 
and  theory  would  be  fully  accounted  for.  It  seems,  however,  that 
the  spores  are  not  small  enough  to  permit  of  our  assuming  slip 
to  the  extent  required. 

The  most  serious  objection  to  my  method  for  testing  Stokes' 
Law  seems  then  to  be  that  it  has  so  far  been  found  impossible 
to  get  the  spores  to  fall  with  a  quite  constant  speed  in  an 
apparently  saturated  chamber.  Now  the  spore  diameters  were 
measured  when  the  spores  were  in  water,  i.e.  when  fully  turgid, 
just  as  spores  are  upon  the  sterigmata  immediately  before  their 
fall.  In  order,  therefore,  to  observe  the  fall  of  the  spores  when 
they  were  in  as  turgid  a  condition  as  possible,  the  two  precautions 
(1)  of  placing  the  field  of  the  microscope  immediately  under  the 
gills,  and  (2)  of  saturating  the  chamber  so  far  as  possible  with 
water-vapour,  were  taken.  If  the  velocity  of  the  spores  could 
have  been  measured  immediately  they  left  the  sterigmata  instead 
of  when  they  came  into  view  beneath  the  gills,  probably  it  would 
have  proved  even  greater  than  that  recorded. 

All  the  measurements  for  density,  size,  and  velocity  of  the 
spores  could  be  made  with  great  exactness.  It  seems  to  me 
most  unlikely  that  the  large  discrepancy  between  theory  and 
observation  can  be  due  to  errors  in  these  measurements.  Unless 
loss  of  water  from  the  spores  in  some  way  is  capable  of  accel- 
erating their  rate  of  fall,  for  the  present  it  would  seem  as  though 
the  spore-fall  method  of  testing  Stokes'  Law  shows  that  the 
actual  velocity  of  fall  of  spheres  about  10  /A  in  diameter  is  some 
50  per  cent,  greater  than  the  Law  demands. 

The  appended  Table,  giving  the  results  of  observations  upon 
the  rates  of  fall  of  spores  of  various  species,  was  compiled  before 
the  tests  for  Stokes'  Law  were  made.  The  air  in  the  chamber  of 
the  compressor  cell  was  not  saturated  and  simply  contained  the 
required  piece  of  fungus.  The  field  of  the  microscope  was 
usually  near  the  gills.  The  rates  of  fall  of  spores  of  a  single 
fruit-body,  as  the  spores  dry  up,  gradually  decrease  after  the  spores 
have  left  the  gills.  The  figures  given  in  the  Table  serve  merely 


THE  RATE  OF  FALL  OF  SPORES 


175 


to  show  the  speed  of  fall  of  the  spores  at  a  certain  distance  from 
the  gills  in  the  unsaturated  air  of  the  chamber.  If  V  be  the 
velocity  of  a  spore  when  fully  expanded  by  osmotic  pressure, 
i.e.  just  after  liberation,  and  V  be  the  velocity  of  the  same  spore 
when  it  has  dried  up,  then  the  velocities  given  in  the  Table  lie 
between  V  and  V.  The  value  of  V,  as  further  experiments  have 
shown,  may  be  as  much  as  3V.  It  will  doubtless  be  different 
for  each  species,  but  it  is  evident,  from  results  given  in  the 
Tables  in  the  next  chapter,  that  up  to  60  per  cent,  should  be 
added  on  to  the  velocities  given  in  the  present  Table  in  order 
to  obtain  approximately  the  true  rate  of  fall  of  the  fully  turgid 
spores  of  which  the  dimensions  are  given.  On  the  other  hand, 
if,  one  wishes  to  calculate  the  velocity  of  the  spores  when  dried 
up,  as  they  must  often  be  in  nature  within  one  or  a  few  minutes 
of  leaving  the  fruit-body,  one  must  subtract  up  to  60  per  cent, 
of  the  velocities  determined. 


Species. 

Spore  Dimensions  in  p. 

Velocity  of 
Fall  in  mm. 
per  Second. 

Loner  Axis. 

Short  Axis. 

Collybia  dryophila 

5-44 

3-23 

0-49 

Pluteus  cervinus 

5-95 

4-57 

0-67 

Psalliota  campestris  : 

Grown  on  a  bed,  I.   . 

7-26 

5-35 

1-06 

„       „     II. 

7-32 

5-64 

1-30 

From  a  field,        III. 

9-7 

5-80 

1-61 

Polyporus  squamosus  . 
Boletus  badius     . 

14-6 

12-8 

5-12 
4-29 

1-03 
1-09 

Paxillus  involutus 

7-48 

4-88 

MO 

Boletus  felleus     . 

1459 

3-78 

1-22 

Marasmius  oreades 

9-5 

5-6 

1-34 

Russula  emetica  . 

8-82 

7-50 

1-64 

Amanita  rubescens 

9-38 

6-53 

1-54 

Galera  tenera 

10-47 

606 

2-13 

Amanitopsis  vaginata 

9-64 

9-64 

2-95 

Coprinus  comatus                  .            |       12-55 

7-48 

3-96 

Coprinus  plicatilis 

12-9      107 

7-9 

4-29 

It  was  found  possible  to  measure  the  rates  of  fall  of  individual 
spores  over  longer  distances  than  4'55  mm.  in  the  following 
manner.  A  field  just  below  the  gills  in  the  compressor  cell  was 
focussed  with  the  horizontal  microscope.  When  a  spore  crossed 
the  upper  line,  a  drum  contact  was  made  by  depressing  the  knob 


1 76  RESEARCHES  ON  FUNGI 

of  the  tapping  key  with  the  left  hand.  The  microscope  was  then 
lowered  with  the  right  hand  by  means  of  a  rackwork  on  the 
stand  so  that  the  spore  was  still  kept  in  view.  When  the  field 
arrived  at  the  bottom  of  the  compressor  cell  after  having  been 
lowered  in  this  way  for  about  8  mm.,  the  spore  crossed  the  lower 
line  of  the  field,  whereupon  a  second  drum  contact  was  made. 
The  time  of  fall  could  therefore  be  calculated  from  the  drum 
record  in  the  usual  way.  The  distance  of  fall  could  be  deter- 
mined by  adding  to  the  distance  between  the  upper  and  lower 
lines  of  the  field,  namely  4'55  mm.,  the  distance  through  which 
the  microscope  had  been  lowered.  The  latter  was  found  in  each 
case  by  reading  a  vertical  scale  which  was  situated  on  the 
microscope  stand  and  provided  with  a  vernier.  From  the  time 
and  distance  data  thus  obtained  the  velocity  of  fall  could  be 
calculated  at  once. 

Fifty  measurements  with  the  spores  of  Boletus  felleus  were  made 
in  the  manner  just  described.  The  average  observed  distance  of 
fall  was  12'05  mm.  and  the  average  time  required  to  fall  through 
it  10'57  seconds.  Hence,  the  average  velocity  of  fall  through 
12-05  mm.  below  the  gills  was  114  mm.  per  second.  Doubtless  by 
this  method  the  rate  of  fall  of  small  particles  might  be  measured 
through  greater  distances  than  12  mm. 

Whilst  measuring  the  rates  of  fall  of  spores  the  magnification 
was  kept  as  low  as  practicable,  so  that  the  observed  distance  of 
fall  should  be  as  large  as  possible.  Under  those  conditions  the 
spores  were  seen  merely  as  just  visible  specks,  the  shape  of  which 
could  not  be  determined.  It  seemed,  however,  of  interest  to 
attainpt  to  find  out  what  positions  the  spores  assumed  whilst 
falling.  The  magnification  of  the  microscope,  therefore,  was 
increased  by  using  a  No.  3  Leitz  objective.  Into  the  much 
lessened  field  of  view,  spores  in  focus  fell  relatively  less  often, 
and  in  passing  across  the  field  appeared  to  fall  with  a  relatively 
much  greater  velocity.  However,  the  shape  of  the  spores  could 
often  be  distinctly  observed.  It  was  found  that  the  spores,  whilst 
falling  the  first  few  millimetres  after  leaving  the  gills,  often  turn 
round  and  round  upon  themselves  in  an  irregular  manner.  Longer 
spores  often  oscillate  from  side  to  side  and  probably  fall  in  very 


THE  RATE  OF  FALL  OF  SPORES       177 

steep  corkscrew-like  paths.  Special  attention  was  paid  to  the 
fall  of  the  spores  of  Polyporus  squamosus,  which  are  nearly 
three  times  as  long  as  they  are  wide.  It  was  found  that  on 
emerging  from  the  hymenial  tubes  many  of  them  have  their 
long  axes  nearly  vertical,  and  that  whilst  falling  they  often 
appear  to  turn  over  and  over  on  themselves  or  to  rock  from  side 
to  side.  However,  by  following  the  spores  individually  with  the 
help  of  a  mechanical  stage,  it  was  plainly  seen  that  after  falling 
about  5  mm.  they  were  almost  without  exception  nearly  or  quite 
horizontal,  and  that  they  then  rotated  in  a  horizontal  plane  very 
slowly  or  not  at  all.  The  final  position  which  the  spores  took  up 
in  still  air  was  therefore  such  that  the  greatest  surface  was 
presented  to  the  resistance  of  the  air.  We  may  conclude,  there- 
fore, that  long  spores  tend  to  fall  in  a  similar  manner  to  that 
assumed  for  the  simple,  prismatic  ice-crystals  which  cause  the 
phenomena  of  sun-dogs,  &c.,  in  northern  regions. 


APPENDIX 

The  compressor-cell  method  of  measuring  the  rate  of  fall  of  spores  was 
devised  in  1905.  I  then  came  to  the  conclusion  that  the  spores  of  Hymenomy- 
cetes  fall  at  a  rate  which  is  roughly  in  accordance  with  Stokes'  formula, 
and  this  fact  was  announced  by  A.  J.  Ewart  in  his  translation  of  PfefFer's 
Physiology  of  Plants.1  During  the  summer  of  1906,  I  carried  out  a  large 
number  of  measurements  of  the  size,  specific  gravity,  and  terminal  velocity 
of  spores,  and  in  1907  Chapters  XIII.,  XIV.,  and  XV.  were  communicated  to 
the  Royal  Society  as  sections  of  a  paper  which  I  subsequently  withdrew.2 

Recently  Zeleny  and  M'Keehan 3  of  the  University  of  Minnesota  have 
announced  that  they  have  made  a  direct  test  of  Stokes'  formula  by  using 
lycopodium  power.  Their  method  of  measuring  terminal  velocity  consisted 
in  allowing  the  powder  to  fall  in  wide  tubes  and  noting  the  rate  of  movement 

1  Vol.  iii.,  1906,  p.  416. 

2  The  paper  called  "  The  Production,  Liberation,  and  Dispersion  of  the  Spores 
of  Hymenomycetes  "  was  accepted  for  publication  in  the  Philosophical  Transactions 
of  the  Royal  Society,  but  on  conditions  which  I  was  unable  to  accept. 

3  John  Zeleny  and  L.  W.  M'Keehan,  "An  Experimental  Determination  of  the 
Terminal  Velocity  of  Fall  of  Small  Spheres  in  Air."    A  paper  read  at  the  meeting 
of  the  American  Association  for  the  Advancement  of  Science,  held  December  1908. 
Abstract  in  Science,  March  19,  1909. 

M 


1 78  RESEARCHES   ON   FUNGI 

of  the  centre  of  the  cloud.     They  came  to  the  conclusion  that  for  lycopodium 
spores  the  formula  gives  velocities  50  per  cent,  in  excess  of  those  observed. 

My  method  for  testing  Stokes'  formula  appears  to  have  various  advantages 
over  that  used  by  Zeleny  and  M'Keehan  for  the  following  reasons.  Amani- 
topsis  spores  have  smooth  walls  and  are  practically  truly  spherical,  whereas 
lycopodium  spores  have  sculptured  walls  and  are  four-sided.  Amanitopsis 
spores  have  a  diameter  only  about  one-third  as  great  as  lycopodium  spores. 
In  the  tube  method  convection  currents  cannot  be  eliminated,  and  it  must 
surely  be  somewhat  difficult  to  decide  the  exact  centre  of  the  spore  clouds. 
By  my  method  of  using  a  very  small  chamber,  the  difficulty  of  convection 
currents  was  reduced  so  as  to  be  negligible,  and  the  velocities  of  the  individual 
spores  could  be  measured  with  considerable  accuracy.  Amanitopsis  spores  are 
liberated  spontaneously  by  the  fungus,  whereas  lycopodium  powder  requires  to 
be  set  in  motion  by  artificial  means.1 

1  The  substance  of  this  Appendix  is  contained  in  a  letter  to  Nature  on  "  The 
Rate  of  Fall  of  Fungus  Spores  in  Air,"  April  14,  1909. 


CHAPTER   XVI 

THE  EFFECT  OF  HUMIDITY  ON  THE  RATE  OF  FALL  OF  SPORES 

IT  can  be  shown  on  mathematical  grounds  that,  when  bodies 
the  size  of  spores  are  allowed  to  fall  freely  in  still  air,  they  reach 
their  constant  terminal  velocity  before  they  have  gone  their  own 
diameter  or  a  distance  of  less  than  10  fi.1  It  was  expected 
at  first,  therefore,  that  a  spore  would  fall  through  the  space  in  a 
Compressor  cell,  i.e.  a  distance  of  about  13  mm.,  at  a  uniform 
speed.  Accordingly,  in  order  to  test  this  supposition,  the  rate  of 
fall  of  spores  through  a  field  of  4-55  mm.  at  different  distances 
below  the  gills  was  measured.  It  was  soon  discovered  that  the 
velocity  of  a  spore  gradually  diminished  as  the  spore  fell  after 
emerging  from  the  gills.  It  was  suspected  that  this  was  due  to 
the  gradual  diminution  in  size  of  the  spore  owing  to  loss  of  water 
from  it  by  drying.  Comparative  experiments  with  the  air  in  the 
chamber  in  different  states  of  humidity  were  then  undertaken. 
The  air  of  the  chamber  was  first  made  as  moist  as  possible  by 
means  of  soaked  blotting-paper,  next  the  ordinary  air  of  the 
laboratory  was  employed,  and  finally  the  air  was  dried  as  far  as 
possible  with  crystals  of  calcium  chloride.  A  different  piece  of 
the  same  fruit-body  was  used  in  each  case.  The  results  of  the 
observations  are  recorded  in  the  Tables  on  p.  180.  The  figures  give 
the  velocities  in  millimetres  per  second. 

From  these  results  we  may  conclude  that,  as  a  general  rule, 
the  spores  fall  most  rapidly  on  leaving  the  gills,  and  that  the  rate 
of  fall  gradually  diminishes.  This  appears  to  be  so,  even  in 
chambers  which  contain  a  free  drop  of  water  and  soaked  blot- 
ting-paper (Fig.  58,  p.  167),  and  in  which  the  air  must  therefore 
be  saturated  with  moisture.  The  tiny  oval  spores  seem  to  be 
capable  of  giving  off  water  vapour  in  an  atmosphere  saturated  so 
far  as  flat  surfaces  are  concerned. 


1  Vide  infra,  Chap.  XVII. 

'79 


1 8o 


RESEARCHES  ON  FUNGI 


It  is  also  evident  that  the  dryer  the  air,  the  more  slowly  do 
the  spores  fall.  At  the  same  distance  from  the  gills,  for  Cuttybia 
dryophila,  the  velocity  of  fall  in  a  dry  chamber  was  only  about 

Collybia  dryophila 


Field. 
Touching  gills 

Soaked  Blotting-paper  in 
Chamber. 

Ordinary  Air 
of 
Laboratory. 

Crystals  of 
Calcium 
Chloride  iu 
Chamber. 

At  First. 

Two  Hours 
Later. 

0-73                    0-87 

0-49 

0-34 

5  mm.  lower    . 

0-72 

0-74 

0-39 

0-28 

10  mm.  lower  . 

0-68 

0-37 

0-27 

Polyporus  squamosus 


Field. 

Soaked  Blotting- 
paper  in 
Chamber. 

Ordinary  Air  of 
Laboratory. 

Crystals  of 
Calcium  Chloride 
in  Chamber. 

Touching  gills  . 

1-83 

1-34 

0-85 

3  mm.  lower 

1-85 

1-25 

0-71 

6  mm.  lower 

1-73 

1-17 

0-70 

7'5  mm.  lower   . 

... 

... 

0-65 
Field  just 
above  crystals 

Psalliota  campestris 


Field. 

Soaked  Blotting- 
paper  in  Chamber. 

Ordinary  Air 
of  Laboratory. 

Touching  gills 

1-48 

1-27 

3  mm.  lower  .... 

U^ 

1-47 

1-20 

6  mm.  lower  .... 

1-39 

1-19 

one-half  of  that  in  a  moist  chamber  containing  wet  blotting-paper. 
In  the  most  dried  condition  the  spores  were  falling  at  only  one- 
third  the  speed  at  which  they  fell  in  the  most  moist  condition. 
The   obvious   explanation   of  the   decrease   in   speed   of  spores 


THE   EFFECT   OF   HUMIDITY 


181 


after  leaving  the  gills,  seems  to  be  that  the  spores  diminish  in 
size  owing  to  the  loss  of  water.  According  to  Stokes'  Law  the 
velocity  varies  as  the  square  of  the  radius  of  a  sphere.  One  must 
remember  that  a  spore  has  an  enormous  surface  compared  with 
its  mass,  and  therefore,  when  falling,  can  readily  and  quickly  part 
with  some  of  its  contained  water.  In  falling  5  mm.  in  ordinary 
air,  when  leaving  the  gills,  spores  of  Collybia  dryophila  (the 
smallest  with  which  I  have  yet  worked)  were  found  to  lose  20P4 
per  cent,  of  their  velocity ;  in  falling  6  mm.  the  spores  of 
Polyporus  squamosus  lost  12' 7  per  cent.,  and  those  of  Psalliota 
campestris  6 -3  per  cent.  The  results  are  collected  in  the  following 
Table  :— 

Diminution  in  Velocity  of  Falling  Spores 


Distance  of 
Species.                                   Fall  in 
Millimetres. 

Time  in 
Seconds. 

Diminution  of 
Velocity 
expressed  in 
Percentage  of 
Initial  Velocity 
observed. 

Collybia  dryophila                      .  ;           5 

11-4 

20-4 

Polyporus  squamosus         .         .              6 

4-8 

12-7 

Psalliota  campestris          .         .  I           6 

4-8 

6-3 

Further  observations  were  then  made  upon  decrease  in  velocity 
when  spores  were  allowed  to  fall  through  a  distance  of  15  cm. 
For  this  purpose  a  brass  chamber  (Fig.  62)  was  constructed. 
The  space  within  it  was  16  cm.  long,  1*1  cm.  wide,  and  0*6  cm. 
deep.  To  one  side  of  the  chamber  a  glass  plate  was  fixed  with 
cement,  and  to  the  other  side  a  long  cover-glass  could  be  affixed 
with  vaseline.  A  piece  of  the  fungus  fruit-body,  which  included 
parts  of  three  or  four  gills,  was  placed  in  the  chamber  at  one 
end.  When  the  latter  was  set  in  the  upright  position,  spores 
fell  from  top  to  bottom.  With  the  horizontal  microscope,  obser- 
vations on  the  velocity  of  the  spores  were  made  at  different 
distances  from  the  gills. 

The  retardation  in  the  velocity  of  fall  was  found  to  be  most 
rapid  immediately  after  the  spores  had  left  the  gills,  and  to 


I  82 


RESEARCHES   ON  FUNGI 


continue    in    a    more   or    less   marked    manner   for   about   10   cm. 

A  final,  terminal,  and  fairly  uniform  velocity  was  then  reached, 
the  time  required  for  its  attainment  being  less 
than  half  a  minute  after  the  spores  had  been 
liberated  from  the  gills.  The  following  curves 
(Fig.  63)  give  the  results  of  the  observations. 
Each  velocity  plotted  is  the  average  of  about 
twenty-five  velocities  recorded  in  sequence. 

The  curve  for  the  Mushroom  spores  is  re- 
markable in  that  it  first  of  all  sinks  and  then 
rises  again.  Possibly  this  is  accounted  for  on 
the  supposition  that  the  spores  buckle  up 
after  a  certain  stage  of  desiccation  has  been 
reached.  Such  a  mode  of  contraction  would 
decrease  the  surface  exposed  in  falling,  and 
thus  increase  the  velocity.  As  a  matter  of 
fact,  Mushroom  spores,  when  drying  on  a  glass 
slide,  rapidly  become  indented  on  one  side  so 
that  they  more  or  less  assume  the  form  of  a 
boat. 

A  general  conclusion  which  may  be  arrived 
at  from  the  data  contained  in  this  chapter 
is,  that  in  nature  spores  fall  most  rapidly 

FIG.  02.— Plan  and        ,          L     .  ,.        ,         *  ...  .  .  , 

section  of  a  long  almost  immediately  alter  liberation  from  the 
meaaTurTngSedtfhe  sterigmata  whilst  they  are  passing  out  from 
rates  of  fall  of  the  fruit-bodies  between  gills,  down  tubes,  &c., 

spores  at  different  . 

distances  from  the  and  that  after  they  have  drifted  in  the  COn- 
gills.  b,  brass :  r  u  r  i_ 

g,  glass  •,  p,  piece  vection  currents  or  the  outer  air  tor  about 
of  pileus.  At  s  haif  a  minute,  they  reach  a  steady  terminal 

and  t  are  shown  » 

two  fields  as  seen     velocity    considerably    less    than     the     initial. 

with  the  horizon- 

tai  microscope  6  We  can  only  suppose  that  at  the  moment  or 
below111  the  "gills  liberation  the  spores  are  fully  turgid,  and  that 
respectively.  One-  by  the  rapid  loss  of  water  they  become  dried 

half  actual  size.  J  J 

up  in  less  than  a  minute.  It  is  certainly  a 
good  arrangement  that  the  spores  should  fall  down  between  the 
gills  or  in  hymenial  tubes,  &c.,  with  the  greatest  velocity,  for 
they  thus  escape  from  the  fruit-bodies  with  the  least  risk  of 


THE   EFFECT   OF  HUMIDITY 


183 


very  small  convection  currents  causing  them  to  touch  the 
hymenium,  to  which,  owing  to  their  adhesiveness,  they  would 
become  firmly  attached.  After  liberation  from  the  fruit-body 


PotlfyVKA 


3         o          78         T        /O       // 

Distance  beloio  gills  in  centimetres. 


f3       /If. 


FIG.  63.  —  Curves  showing  the  rate  of  fall  of  spores  at  various  distances  below  the 
gills  in  a  long  chamber. 

the  spores  fall  much  more  slowly.  This  enables  the  wind  to 
carry  them  much  further  than  would  be  possible  if  no  decrease 
in  velocity  were  to  take  place. 

NOTE.  —  The  gradual  decrease  in  the  rate  of  fall  of  spores  in  a  chamber 
saturated  with  water-vapour  finds  its  readiest  explanation  in  the  supposition 
that  the  spores  gradually  become  smaller  owing  to  loss  of  water.  The  assumption 
that  the  spores  lose  water  in  a  saturated  atmosphere  is  in  harmony  with  the 
well-known  fact  that  the  vapour  pressure  of  a  drop  of  liquid  depends  on  the 
amount  of  curvature  of  its  surface.  The  greater  the  curvature,  the  greater  is 
the  vapour  pressure.  This  is  illustrated  by  the  following  experiment.  If  a 
small  piece  of  sulphur  is  placed  in  a  tube  which  is  then  evacuated  and  sealed, 
and  if  the  tube  is  gently  heated  near  the  sulphur,  the  latter  condenses  on  the 
cool  part  of  the  tube  in  the  form  of  a  great  number  of  very  small  drops  of 
different  sizes.  In  the  course  of  a  day  or  so,  one  finds  that  the  larger  drops 
have  become  still  larger,  and  that  they  have  a  clear  space  round  them.  The 
clear  space  gradually  grows  bigger.  The  explanation  of  this  phenomenon  is 
that  the  smaller  drops  with  the  greater  vapour  pressure  distil  over  into  the 
larger  drops  with  the  smaller  vapour  pressure.  Similarly  we  may  suppose  that 
the  large  free  drop  of  water  in  the  compressor  cell  (Fig.  58,  w,  p.  167)  grows  at 
the  expense  of  water  lost  by  the  minute  falling  spores  owing  to  the  great  differ- 
ence in  the  curvature  of  the  surfaces. 


CHAPTER   XVII 

THE  PATH  OF  THE  SPORES  BETWEEN  THE  GILLS,  ETC.—  THE 
SPORABOLA-  APPENDIX  ON  THE  MOTION  OF  A  SPHERE  IN  A 
VISCOUS  MEDIUM 

BY  methods  already  explained,  it  has  been  shown  that  it  is  possible 
to  determine  by  observation  (1)  the  maximum  horizontal  distance 
to  which  a  spore  travels  when  it  has  been  shot  out  horizontally 
from  a  basidium  lying  in  the  hymenium  of  a  gill,1  and  (2)  the 
terminal  vertical  velocity  with  which  the  spore  falls  toward  the 
earth.2  With  a  knowledge  of  these  data,  and  assuming  that  the 
resistance  of  the  air  is  proportional  to  the  velocity,  it  is  possible 
to  calculate  the  initial  velocity  with  which  a  spore  is  shot  off  its 
sterigma,  and  also  to  map  out  the  trajectory  described. 

The  initial  velocity  with  which  a  spore  leaves  its  sterigma, 
when  projected  in  a  horizontal  direction,  may  be  calculated  as 
follows  :  — 

Let  V=the  terminal  vertical  velocity, 

X  =  the  maximum  horizontal  distance  of  projection, 
H  —  the  initial  horizontal  velocity,  and 
<jr  =  the  acceleration  due  to  gravity. 

It  can  be  shown3  that 


For  spores  of  Amanitopsis  vaginata,  it  has  been  observed  that 
X  =  0'02  cm.  and  V  =  0*5  cm.  per  second  approximately,  whence 

H  =  981xO-02 
0-5 

i.e.  the  spores  are  projected  in  the  horizontal  direction  from  the 
sterigmata  with  an   initial  velocity  of  approximately  40  cm.   per 

1  Method  II.,  Chap.  XI.  a  Chap.  XV. 

3  A  note  on  the  motion  of  a  sphere  in  a  viscous  medium  is  given  in  the 
Appendix  to  this  chapter  for  convenience  of  reference. 

184 


THE   SPORABOLA 


185 


second.  Since  the  maximum  horizontal  distance  of  projection 
is  0'02  cm.,  it  is  clear  that  in  travelling  only  this  short  distance 
the  horizontal  velocity  of  a  spore  is  reduced  from  40  cm.  per 
second  to  zero.  This  will  not  seem  surprising  when  the  ratio 
of  the  surface  to  the  mass  of  the  spore  is  taken  into  account. 

Since  the  spores  are  shot  outwards  horizontally,  they  describe 
a  curved  trajectory  in  falling  toward  the  earth.  The  trajectory 
is  a  peculiar  one.  In  future  it  will  be  referred  to  as  the  sporabola. 

It  can  be  shown  that  the  equation  for  the  sporabola  is 


0  01 


00*. 


where  V  =  the  terminal  vertical  velocity, 

X  =  the  maximum  horizontal  distance  of  projection, 
g  =  the  acceleration  due  to  gravity, 

t/  =  the  distance  of  a  point  on  the  sporabola  below  the  highest  point,  and 
z= the  distance  of  a  point  on  the  sporabola  from  the  vertical  axis. 

Since  V,  X,  and  g  are  known,  by  assuming  values  for  x  correspond- 
ing values  for  y 
can  be  calculated  ° 
and  the  sporabola 
plotted  out.  The 
accom  panying 
figure  represents 
the  sporabolas  for 
A  manitopsis  vagi- 
nata  and  Psalliota 
campestris  (Fig. 
64). 

The  sporabola 
is  remarkable  in 
that  the  horizontal 
part  passes  very 
sharply  into  the 
vertical  part.  The 

horizontal     and    Flo   64  _ The  sporabolas  of  two  spores  shot  out  horizontally 
Vertical       motions  from  the  hymenium.     The  spores,  drawn  to   scale,  are 

shown  below.     The  scale  is  in  centimetres. 

appear   to   be   al- 
most independent  of  one  another.     Direct  inspection  of  the  curve 


1 86 


RESEARCHES   ON   FUNGI 


7 


indicates  that  the  horizontal  velocity  is  reduced  to  zero  by  the 
time  the  spore  has  fallen  through  a  distance  only  about  equal 
to  its  diameter. 

It  must  often  happen  that  spores  are  not  shot  outwards  in 
exactly  the  horizontal  direction  but  at  a  greater  or  less  angle 
thereto.  The  paths  of  spores  projected  with  equal  velocities 
at  various  angles  can  be  deduced  mathematically,  and  are  indi- 
_^  cated  diagrammatically  in  the  ad- 
joining figure  (Fig.  65).  That  the 
sporabola  appears  to  consist  of  two 
parts,  one  due  to  violent  projection 
of  a  spore  and  the  other  due  to 
gravitation,  again  becomes  obvious. 
We  may  conclude  that,  if  a  basidium 
looks  upwards,  it  will  shoot  its  spores 
to  a  height  approximately  equal  to 
the  maximum  horizontal  distance  to 
which  it  would  have  projected  them 
if  it  had  been  placed  horizontally 
FIG  65.-Sporaboias  of  spores  shot  instead  of  vertically.  Quite  generally, 

outwards  from  a  point  at  various  * 

angles  with  the  vertical  and  with    the  sudden  bend  in   each  sporabola 

equal  initial  velocities.  .  .  -11 

takes  place  at  approximately  the  same 

distance  from  the  point  of  projection  at  the  surface  of  a  limiting 
sphere  (Fig.  65). 

Before  attaining  its  steady  terminal  velocity,  a  spore  requires  to 
fall  but  a  very  minute  distance.     This  may  be  shown  as  follows : — 

Let  X  =  the  maximum  horizontal  distance  of  projection, 

x  =  the  distance  of  a  point  on  the  sporabola  from  the  vertical  axis, 
V  =  the  terminal  vertical  velocity,  and 
v  =  the  vertical  velocity  at  any  time. 


Then  it  may  be  deduced  that 


X  _  V 

X~V 


By  substituting  the  value  of  ^  in  the  equation  for  a  sporabola 
we  get 


THE   SPORABOLA  187 

Let  us  assume  that  the  vertical  velocity  at  any  time  is  within 
1  per  cent,  of  the  terminal  velocity,  and  that  y  is  the  distance 
the  spore  has  fallen  before  attaining  this  velocity,  then  putting 
log,  =  2-3  Iog10  and  ^  =  0'99,  we  get 

y= Y."  |  -  log,0  (0-01)  2-3  -  0-99  | 

For  Amanitopsis  vaginata,  since  V  =  O5  cm.  per  second,  we  find 
that 

y  =  0-0009  cm.  =  9  p. 

The  diameter  of  a  spore  is  approximately  10  /*.  Hence  we  can 
state  that  the  distance  fallen  by  a  spore  of  A.  vaginata  before 
reaching  its  terminal  velocity  (within  1  per  cent.)  is  less  than  its 
diameter. 

The  length  of  time  required  for  any  spore  after  being  set  free 
to  attain  its  terminal  vertical  velocity  within  1  per  cent.,  can  be 
shown  to  be  equal  to  0'0047  x  V,  where  V  is  the  terminal  velocity. 
For  Amanitopsis  vaginata  the  terminal  velocity  may  be  taken  as  0-5 
cm.  per  second.  It  can  be  calculated,  therefore,  that  a  spore  would 
attain  its  terminal  vertical  velocity  in  approximately  ^^  second. 
The  terminal  velocities  of  fall  of  the  spores  of  other  species  are  of 
the  same  order  as  that  of  Amanitopsis  vaginata.  We  are  therefore 
justified  in  drawing  the  general  conclusion  that  the  spores  of 
Hymenomycetes  attain  a  uniform  velocity  of  fall  practically  at  the 
instant  of  their  liberation. 

We  can  also  calculate  the  length  of  time  required  for  a  spore  to 
arrive  within  1  per  cent,  of  the  total  horizontal  distance  to  which 
it  is  projected.  At  the  end  of  the  time  in  question,  the  position  of 
the  spore  on  the  sporabola  will  be  x  cms.  from  the  vertical  axis 
and  y  cms.  below  the  highest  point.  According  to  our  assump- 
tion x  =  0-99.  By  substitution  in  the  equation  for  a  sporabola  we 

.X. 

find  that 

y  =  0-0009  cm.  =  9  p. 

It  has  been  shown,  however,  that  a  spore  falls  through  this 
distance  in  approximately  -^  second.  We  may  conclude,  therefore, 
that  the  spore  will  have  travelled  for  only  T^7  second  before  arriving 


1 88  RESEARCHES   ON   FUNGI 

within  1  per  cent,  of  the  total  horizontal  distance  to  which  it  is 
projected.  An  important  conclusion  which  may  be  drawn  from  this 
calculation  is  that  it  would  be  extremely  difficult,  if  not  impossible, 
to  observe  the  horizontal  flight  of  the  spores.  The  horizontal  move- 
ment is  completed  in  ^^  second.  It  is  very  questionable  if  the 
human  eye  could  observe  such  a  movement  of  a  dark  body  at  all, 
and  particularly  under  the  conditions  of  observation  necessitated  by 
the  size  of  the  spores,  the  position  of  the  basidia,  and  the  uncertainty 
of  the  time  of  spore-discharge.  These  theoretical  considerations  fall 
in  line  with  my  observations,  for  I  have  never  yet  succeeded  in 
watching  the  horizontal  flight  of  a  spore  from  its  sterigma. 

The  results  of  the  investigations  upon  the  motion  of  a  spore  of 
AmaniiopeiB  vaginata,  10  /*  in  diameter,  when  projected  from  its 
sterigma  in  a  horizontal  direction,  may  be  summed  up  as  follows : — 

By  observation — 

Maximum  horizontal  distance  of  projection  =  0'02  cm. 

Terminal  velocity  of  fall  =  0'5  cm.  per  second. 
By  calculation — 

The  terminal  velocity  of  fall  is  reached  after  a  distance  of  9  n  (which  is 
less  than  the  diameter  of  a  spore)  has  been  traversed. 

The  terminal  velocity  of  fall  is  reached  in  ^^  second  approximately. 

The  spore  arrives  within  1  per  cent,  of  its  total  horizontal  flight  (i.e.  it 
goes  0*0198  cm.)  in  j^y  second. 

The  initial  horizontal  velocity  is  40  cm.  per  second. 

When  one  compares  the  movement  of  a  spore  with  that  of  a 
pebble  projected  in  like  manner,  the  differences  at  first  appear  to  be 
remarkable.  However,  it  must  be  remembered  that  a  spore  has  an 
enormous  surface  in  proportion  to  its  mass  as  compared  with  a 
pebble.  The  air,  therefore,  in  proportion  to  their  masses,  offers  a 
vastly  greater  resistance  to  the  movement  of  a  spore  than  to  that  of 
a  pebble. 

In  Plate  I.,  Fig.  4,  the  paths  of  spores  between  the  gills  of  a 
Mushroom  are  shown,  whilst  in  the  text-figures  56  (p.  165)  and  66 
similar  illustrations  are  given  for  Amanitopsis  vaginata  and  Poly- 
porus  squamosus  respectively.  It  is  evident  that  the  spores  are 
shot  outwards  from  the  hymenium  in  such  a  manner  that  they  are 
projected  clear  of  the  hymenium  and  yet  not  far  enough  to  strike 
the  opposite  gill.  The  air  is  a  delicate  regulator  in  this  matter. 


THE   SPORABOLA 


189 


The  structure  of  a  Mushroom  is  such  that  the  spores  are  shot  out 
into  the  spaces  between  the  gills,  where  they  fall  down  freely  in 
response  to  gravity.  They  thus  escape  from  the  fruit-body  without 
danger  of  touching,  and  thereby  adhering  to,  the  hyinenium. 

The  hymenium  on  the  side  of  a  gill  may  be  likened  to  a  battery. 
The  basidia  are  the  guns  and  the  spores  the  projectiles.  Each  gun 
is  capable  of  shooting  off  four  projectiles 
in  succession  at  intervals  of  a  few  seconds 
or  minutes.  The  battery  is  so  splendidly 
organised  that  the  guns  are  brought  for- 
ward, mounted,  and  fired  off  in  succes- 
sion. Thus  a  heavy  and  continuous 
boinbardment  is  maintained  for  days  or 
weeks,  and  only  ceases  when  the  am- 
munition has  become  exhausted.  The 
object  of  the  miniature  gunnery  is  to 
drop  the  spores  into  the  spaces  between 
the  gills,  so  that  they  may  fall  out  from 
the  fruit-body  without  touching  one 
another  or  any  part  of  the  hymenium. 
The  success  with  which  a  large  Mush- 
room or  Polyporus  is  able  in  the  course 
of  a  few  days  to  liberate  thousands  of 
millions  of  spores,  and  entrust  them  to 
the  scattering  winds,  may  well  excite  our 
admiration. 

In  a  few  rare  instances,  owing  to 
imperfection  in  the  structure  of  the  pilei,  the  spores  are  not  all 
able  to  escape  into  the  outer  air.  Thus,  for  example,  in  Nolanea 
pascua  the  gills  often  become  locally  powdered  with  the  red  spores. 
This  is  due  to  the  fact  that  the  gills  are  somewhat  wavy,  and  there- 
fore not  properly  disposed  in  vertical  planes.  The  adhesive  spores, 
when  falling,  catch  and  stick  on  the  projecting  parts. 


FIG.  66.— Vertical  section 
through  two  hymenial  tubes 
from  the  pileus  of  Polyporus 
squamosus.  The  arrows  show 
the  sporabolas  described  by 
the  spores  when  they  are 
discharged,  h,  the  hyme- 
nium. About  8  times  natural 
size. 


190  RESEARCHES   ON  FUNGI 


APPENDIX 

THE  MOTION   OF  A   SPHERE   IN  A   VISCOUS  MEDIUM 
Contributed  by  Dr.  GUY  BARLOW. 

(The  notation  is  the  same  as  that  employed  in  Chapters  XV.  and  XVII.) 

As  shown  by  Stokes,  the  resisting  force  on  a  sphere  of  radius  a  when  moving 
with  velocity  v  is  given  by 

Since  the  force  is  directly  proportional  to  the  velocity,  it  is  evident  that  the 
component  of  this  force  in  any  direction  is  also  directly  proportional  to  the 
component  of  the  velocity  in  that  direction.  The  motion  of  the  sphere  when 
projected  under  gravity  can  therefore  be  regarded  as  compounded  of  the 
independent  horizontal  and  vertical  motions,  and  these  may  be  conveniently 
investigated  separately. 

1.  Fall  from  rest  under  gravity. 

The  equation  of  motion  is — 

dv 

m  —j-  =  mg  —  btrfj.av, 

where  m  is  the  mass  of  the  sphere  and  v  its  velocity  downwards  at  time  t. 
The  density  cr  of  the  medium  is  here  neglected. 
This  equation  may  be  written 

dv 

5=*-«»    •        •        •        ...        •        •        (2) 

where 


When  the  steady  terminal  state  is  reached,  _?  -•=  0,  v  =  V,  hence  from  (2), 

V=f       . (3) 

Substituting  value  of  c  and  putting  m  =  ~Tra3p  we  obtain  Stokes'  expression 

O 

for  the  terminal  velocity 

T-|^?.  .        (4, 

Equation  (2)  may  now  be  written — 

5**?* 

Integration  with  initial  condition  v  —  o  when  t  =  o  gives 

v  =  V  (l-e-c') (5) 


THE   MOTION   OF  A   SPHERE  191 

Putting  v  =  -j-  and  integrating  again  with  condition  y  =  o  when  t  =  o  we  get 

y  =  V\t-l-(l-e-«)\       -..        .        .        .        .        (6) 

2.  Horizontal  motion  with  initial  velocity  H. 

If  u  is  horizontal  velocity  at  time  t,  the  equation  of  motion  is  now  simply 

du 

dt=-cu' 
or 

du 

U  -y-  =  -  CM. 

ax 
Therefore 

d«  =  -  cote, 
and  hence 

H-M  =  CX  .  (7) 

But  a;  =  X  for  u  =  o,  therefore  H  =  cX. 

From  the  last  expression  and  (3)  we  obtain 

H=f (8) 

Proceeding  with  the  integration,  from  (7)  we  have 

dx 

~dt=u 
=  H-cx 

=  e(X-z). 

Integration  with  initial  condition  x  =  o  when  t  =  o  leads  to 

*=X(l-e-<*) (9) 

3.  The  equation  of  the  path  of  a  sphere  projected  horizontally  under  gravity 
is  obtained  at  once  by  the  elimination  of  t  from  the  two  equations  (6)  and  (9) ; 
and  replacing  c  by  its  value  ^  we  have  finally 

"7 1  X'-xH!  •  •  •  •  •  (i») 


CHAPTER   XVIII 

THE   ELECTRIC   CHARGES  ON   THE   SPORES 

ALTHOUGH  the  matter  may  be  of  but  small  biological  interest,  it 
seemed  desirable  to  ascertain  whether  or  not  the  falling  spores 
carry  electric  charges,  and,  if  so,  of  what  kind.  The  apparatus  for 
the  investigation  of  the  problem  was  constructed  as  follows.  A 
brass  chamber,  shown  at  B  by  two  sections  in  Fig.  67,  was  supported 
on  a  rod,  R,  and  covered  in  front  and  behind  with  glass  discs,  GG'. 
At  its  centre  were  fixed  two  brass  plates,  PP',  1/2  cm.  wide  and 
2  cm.  high,  so  that  they  were  parallel  to  one  another  and  about 
1*5  mm.  apart.  The  plates  were  attached  to  wires  introduced 
through  lateral  holes  in  the  chamber,  insulation  being  secured  by 
means  of  glass  tubing,  TT',  and  sealing-wax,  S.  Above  the  plate 
was  suspended  a  piece  of  the  pileus  of  a  Mushroom,  F,  with  the 
gills  looking  downwards.  This  was  held  in  position  by  means 
of  a  pin  stuck  into  a  cork,  K,  covered  with  tinfoil,  N.  The  brass 
chamber,  and  thus  also  the  piece  of  fungus,  was  carefully  earthed 
by  means  of  a  wire  attached  to  a  gas-pipe  at  E.  By  means  of 
other  wires  the  two  plates  were  connected  with  a  mercury  com- 
mutator, C.  The  latter  was  then  connected  on  one  side  with  the 
gas-pipe,  E,  and  on  the  other  with  the  city  main,  M,  of  220  volts. 
The  lamp,  L,  was  placed  in  the  circuit  for  the  purpose  of  detecting 
any  accidental  flow  of  current.  By  moving  the  handle  of  the 
commutator  to  the  right,  both  the  piece  of  fungus  and  the  brass 
plates  were  earthed  and  therefore  rendered  neutral,  whilst  by 
moving  it  to  the  left  the  plates  were  given  charges  of  opposite 
signs. 

A  vertical  plane,  passing  between  the  plates  towards  their 
centres,  was  focussed  and  observed  by  means  of  a  horizontal 
microscope  with  a  magnification  of  about  25  and  a  field  of 

view   5'5   mm.   in   diameter   (cf.   Plate   IV.,  Fig.  29).     When   the 

192 


THE  ELECTRIC   CHARGES   ON  THE   SPORES       193 

handle  of  the  commutator  was  turned  to  the  right  so  that  the 
plates  were  uncharged,  the  spores  could  be  seen  falling  vertically 
downwards  between  them  at  the  rate  of  about  1  mm.  per  second. 
No  attraction  of  the  spores  to  the  plates  could  be  detected.  When 
spores  were  observed  to  have  reached  the  centre  of  the  space  between 
the  plates,  the  handle  of  the  commutator  was  suddenly  turned 
to  the  left  so  that  one  of  the  plates  became  positively  and  the 
other  negatively  charged.  Immediately  the  paths  of  most  of  the 
spores  were  altered  (Fig.  68,  A).  Some  spores  were  attracted  to 
one  plate  and  some  to  the  other,  the  majority  going  to  the  one 


FIG.  67. — Apparatus  with  electrical  attachments  for  detecting  the  electrical 
charges  on  falling  spores.  The  brass  chamber  B,  natural  size.  Description 
in  the  text. 

with  a  positive  charge.  A  few  continued  their  motion  vertically 
downwards.  A  number  of  spores  appeared  to  turn  at  right  angles 
to  their  former  courses  and  they  then  moved  with  great  rapidity 
to  the  plates.  These  must  have  been  the  spores  which  were 
relatively  the  most  highly  charged.  Others  made  their  way  to 
the  plates  at  a  more  or  less  gentle  angle  to  the  vertical  and  with 
a  less  accelerated  velocity.  Doubtless  they  were  less  highly 
charged.  A  certain  number  of  spores  which  were  not  appreciably 
affected  by  charging  the  plates  were  probably  not  electrified  at  all. 

On  reaching  one  of  the  plates,  each  spore  became  charged  with 
electricity  of  the  same  sign  as  that  on  the  plate,  and  in  consequence 


194 


RESEARCHES   ON  FUNGI 


tended  to  be  repelled  from  the  latter.  Owing  to  their  adhesiveness, 
however,  the  spores  were  unable  to  leave  the  plates  after  having 
once  come  in  contact  with  them.  When  the  plates  were  left 
charged  for  some  hours,  the  spores,  which  fell  in  large  numbers 
from  the  piece  of  pileus,  gradually  formed  simple  or  branching 
chains  which  sometimes  stretched  almost  from  one  plate  to  the 
other,  thus  indicating  the  direction  of  the  lines  of  force  between 
them.  The  formation  of  chains  not  only  demonstrated  the 


FIG.  68. — The  paths  of  spores  falling  between  two  brass  plates.  A,  shows  how 
the  spores  deviate  from  the  vertical  when  the  plates  are  suddenly  electrified 
with  charges  of  opposite  signs.  B,  zigzag  path  of  a  spore  produced  by 
alternately  reversing  the  charges  on  the  plates.  C,  path  of  a  spore  pro- 
duced by  charging  the  plates,  making  them  neutral,  giving  them  reversed 
charges,  &c.,  in  succession. 

tendency  of  the  spores  to  be  repelled  from  the  plates  and  from 
one  another,  but  also  the  fact  that  the  spores  strongly  adhere 
to  surfaces  with  which  they  may  come  in  contact. 

When  the  plates  were  suddenly  charged,  it  was  found  that 
proximity  of  a  spore  to  one  plate  rather  than  the  other  was  not 
a  factor  deciding  to  which  of  the  two  plates  the  spore  should 
move  (Fig.  68,  A).  There  seems  to  be  no  escape  from  the  conclusion 
that,  either  at  the  moment  of  discharge  from  the  sterigmata  or 
within  a  very  few  seconds  afterwards  whilst  falling  through  the 
air,  the  majority  of  spores  receive  positive  or  negative  electric 


THE   ELECTRIC   CHARGES   ON   THE   SPORES       195 

charges  of  different  strengths,  whilst  a  certain  number  do  not 
become  charged  at  all. 

By  another  arrangement  of  the  commutator,  it  was  possible  to 
reverse  alternately  the  charges  on  the  plates  or  to  remove  them. 
By  reversing  the  charges  alternately  a  spore  can  be  made  to  take 
a  zigzag  path  across  the  field  like  that  shown  in  Fig.  68,  B.  By 
successively  charging  the  plates  H — ,  00,  — K  00,  H — ,  &c.,  one 
can  make  the  path  of  a  spore  still  more  irregular  (Fig.  68,  C). 

Several  other  species  beside  Psalliota  campestris  were  tested, 
among  them  being  Polyporus  squamosus.  In  all  cases  the  spores 
behaved  like  those  of  the  Mushroom,  the  majority  appearing  to 
be  charged,  either  positively  or  negatively. 

That  the  spores  bear  electric  charges  during  their  passage  through 
the  air  may  be  regarded  as  a  physical  fact  of  no  apparent  biological 
importance.  There  seems  to  be  no  reason  to  suppose  that  in 
nature  the  spores,  in  consequence  of  being  electrified,  settle  on 
one  surface  rather  than  another.  It  therefore  appears  improbable 
that  the  charges  are  of  use  to  the  spores  in  enabling  them  to  obtain 
advantageous  locations  for  germination. 

A  further  investigation  as  to  the  manner  in  which  the  spores 
originally  become  charged  and  into  the  conditions  which  determine 
the  gain  or  loss  of  charges  by  them  was  thought  unnecessary  for 
my  present  purpose. 


CHAPTER    XIX 

THE   COPRINUS  TYPE   OF  FRUIT-BODY 

"  And  agarics  and  fungi  with  mildew  and  mould 
Started  like  mist  from  the  wet  ground  cold  ; 
Pale,  fleshy,  as  if  the  decaying  dead 
With  a  spirit  of  growth  had  been  animated  ! 

Their  moss  rotted  off  them,  flake  by  flake, 
Till  the  thick  stalk  stuck  like  a  murderer's  stake, 
Where  rags  of  loose  flesh  yet  tremble  on  high, 
Infecting  the  winds  that  wander  by." 

—SHELLEY.1 

THE  Coprini  are  especially  characterised  by  the  fact  that  the  gills 
"  deliquesce  "  on  maturity,  and  that  drops  of  an  inky -looking  fluid 
are  often  formed  on  the  pilei.  So  far  as  I  am  aware,  however, 
although  many  figures  and  photographs2  of  members  of  the 
Coprinus  genus  have  been  published,  no  one  hitherto  has  ex- 
plained the  real  significance  of  the  fact  of  "  deliquescence  "  or  the 
general  structural  arrangement  of  Coprinus  fruit-bodies.  In  what 
follows,  I  hope  to  be  able  to  show  how  admirably  a  Coprinus 
fruit-body  is  constructed  when  regarded  as  a  highly  efficient 
spore-producing  and  spore-liberating  organ. 

One  of  the  best  known  and  largest  of  the  Coprini  is  Coprinus 
comatus.  It  often  comes  up  in  great  abundance  in  fields 
(Plate  IV.,  Fig.  21).  It  "deliquesces"  in  a  typical  manner. 
Fruit-bodies  of  this  species  afforded  me  admirable  material  for  a 
study  of  the  structure  of  a  Coprinus  in  relation  to  spore-fall. 

1  The  second  of  these  two  verses  evidently  refers  to  a  species  of  Coprinus. 
The  poet  had  probably  noticed  the  remarkable  changes  which  take  place  in  the 
conspicuous  fruit-bodies  of  Coprinus  comatus. 

2  A  series  of   excellent  photographs  of  this  species  has  been  published  by 
G.  F.  Atkinson,  "  Studies  and  Illustrations  of  Mushrooms  :  II.,"  Bull.  168,  Cornell 
Univers.  Agric.  Experiment  Station,  1899;  also,  Mushrooms — Edible,  Poisonous,  dr., 
Ithaca,  1901,  pp.  33-41. 

196 


THE   COPRINUS   TYPE   OF  FRUIT-BODY  197 

An  unripe  pileus  which  has  attained  its  full  length  is  more  or 
less  barrel-shaped  (Plate  II.,  Fig.  7 ;  Plate  IV.,  Figs.  21  and  22,  to 
the  right).  The  gills  are  white  in  colour,  closely  packed  together, 
and  with  very  few  exceptions  equal  in  length. 

Upon  beginning  to  open  out,  the  pileus  alters  its  form  from 
that  of  a  barrel  to  that  of  a  bell  (Plate  IV.,  Figs.  21  and  22; 
Plate  I.,  Fig.  1).  It  breaks  away  from  the  stipe  below  and  leaves 
the  latter  encircled  with  an  annulus.  Whilst  the  gills  are  moving 
radially  outwards  from  the  stipe,  they  become  slightly  separated 
from  one  another.  The  rim  of  the  bell-shaped  pileus  now  turns 
slightly  outwards  (Plate  I.,  Fig.  1).  This  results  in  a  further 
separation  of  the .  lower  ends  of  the  gills,  so  that  the  spaces  which 
have  thus  arisen  between  them  are  similar  to  those  between  the 
gills  throughout  their'  whole  length  in  the  case  of  a  Mushroom 
(cf.  Plate  IV.,  Figs.  23  and  25).  Except  at  their  lower  ends, 
adjacent  gills  at  this  stage  in  development  are  united  by  inter- 
locking cystidia  along  their  margin,  and  are  just  as  closely  packed 
as  they  were  when  the  fruit-body  was  barrel-shaped.  The  separa- 
tion of  the  lower  ends  of  the  gills  is  accompanied  by  the  beginning 
of  the  process  of  "  deliquescence." 

Whilst  the  pileus  is  changing  from  the  barrel  to  the  bell  form 
and  is  separating  the  lower  ends  of  its  gills,  the  basidia  are  rapidly 
developing  their  spores.  As  these  ripen  they  turn  pinkish  and 
finally  black.  Just  before  "deliquescence"  begins,  it  can  clearly 
be  made  out  that  the  spores  ripen  on  the  gills  from  below  up- 
wards. The  lower  parts  of  the  gills  blacken  first  (Plate  I.,  Fig.  1). 
The  black  zone  passes  into  a  pink  zone  higher  up,  and  this  in  its 
turn,  toward  the  top  of  the  pileus,  gradually  shades  into  white. 

Whenever  a  gill  has  become  black,  a  small  piece  of  its  surface, 
when  seen  in  face  view  with  the  microscope,  has  the  appearance 
shown  in  Plate  III.,  Fig.  15.  The  pattern  presented  to  the  eye 
is  very  regular  and  pleasing.  Each  basidium  bears  four  black 
spores,  and  is  separated  from  adjacent  basidia  by  paraphyses. 
The  four  spores  of  a  basidium  are  so  attached  to  the  sterigmata 
that  they  are  separated  from  one  another  as  much  as  possible. 
They  are  thus  prevented  from  touching,  and  consequently  from 
adhering  to,  one  another  both  during  development  and  discharge. 


198 


RESEARCHES   ON   FUNGI 


The  paraphyses  are  present  in  just  the  right  proportion  to  prevent 
the  spores  of  adjacent  basidia  from  coming  in  contact.  A  glance 
at  Plate  III.,  Fig.  15,  shows  that  the  spacing  of  the  adhesive 
spores  is  brought  about  so  economically  that  it  would  be  difficult 
to  imagine  how  more  of  them  could  be  developed  simultaneously 
on  any  given  area  of  a  gill  surface.  A  cross-section  through  a 
gill  (Plate  III.,  Fig.  16)  shows  that  the  basidia  project  considerably 
beyond  the  paraphyses  and  are  all  directed  perpendicularly  out- 
wards from  the  gill  surface. 

When    the    pileus    is    still    barrel-shaped    and    until    spore-fall 


FIG.  69. — Coprinus  romatus.  Fruit-bodies  in  an  early  stage  of  development. 
In  the  tallest  the  fall  of  spores  and  autodigestion  have  just  begun.  The 
four  others  are  a  few  hours  younger :  the  pilei  are  separating  from  the 
stipe  below  and  the  gills  are  still  intact.  Photographed  at  Sutton  Park, 
Warwickshire,  by  J.  E.  Titley.  About  £  natural  size. 

begins,  the  inner  edges  of  the  gills  towards  the  stipe,  throughout 
their  entire  length  and  for  a  width  of  about  O25  mm.,  appear  to 
the  naked  eye  as  white  bands  (Plate  I.,  Fig.  1,  m;  Plate  II., 
Figs.  8  and  9,  ra).  These  are  especially  inflated  portions  of  the 
gills,  entirely  devoid  of  basidia  and  covered  over  by  large,  colour- 
less, unicellular  cystidia  (Plate  III.,  Figs.  13  and  14).  The 


THE   COPRINUS   TYPE   OF  FRUIT-BODY 


199 


thickened  marginal  bands  of  adjacent  gills  are  in  contact  with 
one  another,  so  that  a  solid  white  cylinder  is  formed  which  en- 
sheaths  the  stipe.  It  is  important  to  notice  that  the  gills, 
except  where  they  join  at  the  membranous  flesh  of  the  pileus 
and  are  in  contact  by  means  of  the  inner  inflated  marginal  bands, 


FIG.  70. —  Voprinus  comatua.  Same  fruit-bodies  as  shown  in  Fig.  (>9,  twenty-two 
hours  older.  All  are  shedding  spores  and  undergoing  autodigestion.  The 
pileus  of  the  tallest  has  become  reduced  to  one-half  its  original  size  and  a 
few  drops  of  inky  fluid  have  fallen  from  its  recurved  rim  on  to  the  pilei 
below.  The  stipes  have  lengthened  considerably.  Photographed  at  Button 
Park,  Warwickshire,  by  J.  E.  Titley.  About  ^  natural  size. 

are  separated  throughout  their  entire  length  (Plate  I.,  Fig.  5). 
In  the  spaces  thus  provided  between  the  gills,  the  projecting 
basidia  can  freely  develop  to  maturity  (Plate  III.,  Fig.  14).  It 
thus  happens  that  the  spores  of  basidia,  which  belong  to  adjacent 
gills,  are  never  in  danger  of  coming  into  actual  contact  and  con- 


200  RESEARCHES   ON  FUNGI 

sequently  of  adhering  to  one  another.  The  significance  of  the 
marginal  bands  with  their  cystidia  seems  to  be,  therefore,  that 
they  secure  that  the  faces  of  adjacent  gills,  i.e.  the  hy menial 
surfaces,  shall  be  suitably  spaced  during  development.1 

The  so-called  "  deliquescence "  of  a  Coprinus  fruit-body  has 
nothing  in  common  with  the  phenomenon  of  deliquescence  of 
crystals  known  to  the  chemist.  The  phenomenon  with  which  we 
have  to  deal  is  really  a  process  of  autodigestion.  The  solid  parts 
of  the  gills  become  fluid,  in  all  probability  through  the  agency 
of  digestive  enzymes.  There  is  not  the  slightest  reason  to  suppose 
that  the  fluid  is  derived  from  the  water-vapour  of  the  air. 

Autodigestion  of  a  gill  always  begins  at  its  base,  along  the 
free  edge  where  the  gill  is  separating  or  has  just  separated  from 
its  neighbours  (Plate  II.,  Fig.  8,  s).  The  marginal  cystidia  are 
first  involved.  They  simply  break  down,  become  fluid  and  indis- 
tinguishable. After  the  destruction  of  the  cystidia,  the  auto- 
digestion proceeds  obliquely  upwards  and  gradually  destroys  the 
whole  gill  (Plate  II.,  Figs.  8,  9,  10,  and  11).  The  entire  destruction 
of  the  gills  from  below  upwards  in  large  fruit-bodies  was  observed 
to  take  about  two  days,  whilst  in  smaller  ones  the  process  was 
carried  out  in  little  more  than  twenty-four  hours  (cf.  Figs.  69, 
70,  and  71). 

As  the  gills  get  shorter  and  shorter  owing  to  their  destruction 
from  below  upwards,  the  pileus  gradually  opens.  It  passes  from  the 
bell  shape  to  the  helmet  shape  (Plate  II.,  Fig.  9),  and  at  length, 
as  it  becomes  smaller  and  smaller,  flattens  out  into  a  disc  like 
that  of  a  Mushroom  (Plate  II,  Fig.  10 ;  Plate  IV.,  Figs.  21  and  22). 
The  remains  of  the  gills  thus  come  to  be  held  out  horizontally. 
In  this  position  they  disappear  in  their  entirety,  so  that  merely 
the  naked  central  flesh  of  the  pileus  is  left  behind  (Plate  II,  Fig.  11). 
When  a  fruit-body  has  completely  lost  its  gills,  the  stipe  often 
bends  in  two  toward  the  middle,  so  that  the  pileus  flesh,  which  has 
now  become  very  discoloured  and  ragged,  either  hangs  down  or 

1  It  might  perhaps  be  shown  that  the  provision  of  spaces,  so  that  the  basidia 
can  develop  their  spores  in  air  without  contact  with  any  obstacle,  is  a  principle  of 
development  applying  not  only  to  the  Coprini,  Psalliota,  Polyporus,  &c.,  but  to 
the  Basidiomycetes  generally. 


THE   COPRINUS  TYPE   OF   FRUIT-BODY 


201 


comes  in  contact  with  the  ground.  The  further  destruction  of  the 
fruit-body  appears  to  be  completed  by  putrefaction.  From  the 
first  appearance  of  a  very  young  fruit-body  above  the  ground  up 
to  the  giving  way  of  the  stipe,  the  interval  was  found  to  be  about 
seven  days. 

It    sometimes    happens    that,  shortly   after    autodigestion   has 


FIG.  71. — Coprinus  comatus.  Last  stages  in  autodigestion.  The  fruit-body  to  the  left 
has  lost  about  three-fourths  of  its  pileus  but  is  still  shedding  spores.  The  same 
fruit-body,  twenty-four  hours  older,  is  shown  on  the  right.  The  gills  have  now 
practically  disappeared  and  spore-emission  has  ceased.  Photographed  by  P.  Grafton. 
^  natural  size. 

begun,  the  free  margin  of  the  pileus  presents  a  rayed  or  ragged 
appearance.  This  is  due  to  the  fact  that,  at  intervals  round  the 
base  of  the  pileus,  the  lower  ends  of  individual  gills  have  split 
along  their  median  planes  from  without  inwards,  and  that  the 
two  halves  of  each  gill  so  divided  have  been  pulled  apart  laterally 
(Plate  IV.,  Fig.  23).  The  fissures  seen  at  the  bottom  of  the  pileus 


202  RESEARCHES   OX   FUNGI 

from  without  correspond,  therefore,  not  to  spaces  between  adjacent 
gills,  but  to  spaces  between  half  gills  pulled  asunder. 

During  autodigestion,  the  oblique  free  edge  of  each  gill  is  black 
and  covered  with  a  liquid  film.  From  this  edge  evaporation  takes 
place  and  no  actual  drops  of  inky  fluid  form  upon  it.  The  spaces 
between  the  gills,  therefore,  do  not  become  choked  up,  but  remain 
open  just  as  in  a  Mushroom  (Plate  IV.,  Fig.  23).  As  autodigestion 
proceeds,  each  gill,  when  seen  in  face  view,  gets  narrower  and 
narrower  below,  until  it  is  almost  reduced  to  nothing  (Plate  II.. 
Fig.  8).  The  membranous  flesh  of  the  pileus  bearing  the  remains 
of  the  gills  often  curls  outwards  and  upwards  so  as  to  form  a  neat 
and  curious  circular  roll  (Plate  IV.,  Figs.  22  and  24;  Plate  III, 
Figs.  9  and  10).  Sometimes,  however,  it  simply  hangs  downwards, 
in  which  case  the  pileus  looks  ragged  and  untidy  (Plate  II.,  Fig.  8; 
Plate  IV.,  Fig.  21).  With  the  continuance  of  autodigestion,  the 
now  useless  material  just  described  is  gradually  converted  more  or 
less  completely  into  drops  of  inky-looking  fluid,  which  may  often 
be  seen  hanging  from  the  rim  of  the  pileus  (Plate  II.,  Fig.  10 ; 
Plate  IV.,  Fig.  24).  It  will  shortly  become  clear  that  the  formation 
of  the  circular  roll  on  the  top  of  the  pileus  is  to  be  regarded  as 
an  admirable  method  of  securing  that  that  part  of  the  pileus  which 
has  ceased  to  have  any  functional  significance  shall  be  as  far 
removed  as  possible  from  the  paths  of  the  falling  spores,  and  thus 
prevented  from  hindering  spore-disposal  by  the  wind. 

If  one  allows  an  upright  fruit-body,  with  its  stipe  placed  in  wet 
sand,  to  shed  its  spores  under  a  bell-jar,  one  finds  by  microscopic 
examination  that  the  inky  drops,  produced  by  autodigestion,  consist 
of  a  brown  fluid  containing  granules  but  practically  free  from  spores. 
The  fluid,  therefore,  is  not  made  black  by  spores.  The  colour  is 
probably  due  to  an  oxydase  which  unites  the  oxygen  of  the  air 
with  some  substance  liberated  from  the  dying  cells,  for  it  was 
found  that  the  colourless  juice  squeezed  from  an  unripe  pileus 
turns  brown  in  a  few  hours.1  The  drops  collect  only  on  the  rim  of 
the  pileus,  where  they  do  not  interfere  with  the  liberation  of  the 
spores  into  the  air.  If  paper  is  placed  round  the  base  of  the  stipe, 

1  Cf.  A.  H.  R.  Buller,  "  The  Enzymes  of  Polyporus  squamosus,"  Ann.  of  Bot.y 
vol.  xx.  p.  51. 


THE   COPRINUS  TYPE   OF  FRUIT-BODY  203 

a  black  spore-deposit  collects  upon  it,  which  is  similar  to  that 
produced  under  the  same  conditions  by  an  ordinary  Agaric. 

In  nature,  the  fluid  produced  by  autodigestion  is  largely  got 
rid  of  by  evaporation.  The  amount  of  it  adhering  to  the  pileus 
rim  varies  considerably  according  to  the  state  of  the  weather.  In 
very  dry  weather,  it  often  happens  that  actual  drops  are  not  formed 
at  all.  On  the  other  hand,  dripping  is  favoured  by  a  saturated 
atmosphere,  and  was  found  to  take  place  regularly  with  fruit-bodies 
placed  in  a  damp-chamber. 

Two  independent  observers  have  informed  me  that  they  have 
been  surprised  by  finding  that  the  drops  hanging  from  the  pileus 
of  certain  fruit-bodies  were  red  instead  of  black.  In  one  case  the 
colour  was  described  as  "just  like  that  of  red  currants."  I,  myself, 
have  never  seen  any 'red  drops,  but  can  scarcely  doubt  their 
occasional  occurrence.  Possibly  the  red  drops  were  merely  ex- 
creted from  the  exterior  of  the  pileus  like  those  given  out  by 
Fistulina  hepatica  or  Lentinus  lepideus,  and  they  may  have  had 
no  connection  with  the  process  of  autodigestion. 

A  fruit-body  begins  to  liberate  its  spores  as  soon  as  it  has  become 
bell-shaped  and  the  lower  ends  of  the  gills  have  separated.  The 
spores  are  projected  violently  from  their  sterigmata  into  the  spaces 
between  the  gills,  where  they  describe  sporabolas,  and  thus  escape 
into  the  outer  air.  Proofs  that  the  four  spores  of  a  basidium  are 
shot  off  in  succession  in  the  course  of  a  few  seconds  or  minutes  have 
already  been  given.1  The  nature  of  a  sporabola  has  likewise  been 
dealt  with.2  Convincing  proof  that  the  spores  are  liberated  into  the 
air  may  be  obtained,  not  only  by  collecting  the  thick  black  spore- 
deposit  on  white  paper,  but  also  by  the  beam-of-light  method. 
When  a  fruit-body  is  placed  upright  in  a  closed  beaker,  the  beam 
of  light  reveals  clouds  of  spores  emerging  from  the  gills  and 
becoming  scattered  by  convection  currents  in  the  enclosed  air.3 

Spore-discharge  from  a  gill  is  not  general  all  over  its  surface 
as  in  a  Mushroom,  but  extremely  local.  It  begins  on  both  sides 
simultaneously,  towards  the  base  along  two  opposite  and  very 
narrow  zones  (Plate  II.,  Fig.  8,  s),  which  run  parallel  to  and  adjoin 
the  oblique,  free,  inner  gill  edge.  We  may  refer  to  a  part  of 

1  Chap.  XT.,  Method  IV.  2  Chap.  XVII.  »  Cf.  Chap.  VII. 


204  RESEARCHES   ON  FUNGI 

the  hymenium  where  spore-discharge  is  actively  taking  place  as 
the  zone  of  spore-discharge.  Such  a  zone  may  be  two  or  more 
centimetres  long,  but  it  is  only  a  fraction  of  a  millimetre  wide. 
A  zone  of  a  gill,  where  spore-discharge  is  taking  place  rapidly, 
becomes  entirely  spore-free  owing  to  the  fact  that  all  the  basidia 
within  it  discharge  their  spores  almost  simultaneously.  The  two 
opposite  zones  of  spore-discharge  on  a  gill  gradually  move  upwards 
together  and  parallel  to  themselves.  Thus,  in  the  course  of  about 
two  days,  all  the  spores  on  a  gill  are  successively  discharged  from 
below  upwards. 

With  the  commencement  of  spore-discharge,  or  possibly  just 
previously  thereto,  the  marginal  cystidia  bordering  the  zone  of  spore- 
discharge  break  down,  and  become  fluid  and  unrecognisable.  The 
discharge  of  spores  leads  to  the  production  of  a  zone  of  spore-free 
gill  surface.  Before  this  has  become  0'5  mm.  wide,  it  becomes 
subjected  to  the  process  of  autodigestion.  The  basidia  at  the  gill 
edge,  which  were  the  first  to  discharge  their  spores,  together  with 
the  paraphyses  between  them,  rapidly  lose  their  sharp  contours, 
become  entirely  disorganised,  and  turn  into  fluid.  The  subhymenial 
cells  and  those  of  the  traina  break  down  in  a  similar  manner. 
Thus  the  gill  edge,  for  a  distance  of  about  two  centimetres,  becomes 
converted  into  a  dark  liquid  film  (Plate  II.,  Fig.  8,  a).  We  can 
now  distinguish  five  zones  on  each  surface  of  a  gill,  running  parallel 
to  its  oblique  edge  (Plate  II.,  Fig.  12).  Highest  of  all  is  a  zone  with 
basidia  bearing  ripe  spores.  Below  this  is  the  narrow  zone  of  spore- 
discharge,  where  the  basidia  are  all  rapidly  freeing  themselves  of 
their  spores,  by  shooting  them  out  one  by  one  into  the  interlamellar 
spaces.  Further  below,  there  is  a  narrow  zone  of  spore-freed  surface 
where  the  basidia  all  have  naked  sterigmata.  Below  this  again 
is  the  zone  of  autodigestion  where  the  basidia  and  paraphyses 
are  becoming  disorganised  and  liquefied.  Finally,  occupying  the 
extreme  gill  edge,  there  is  a  dark-coloured,  adhesive,  liquid  film. 

By  watching  a  piece  of  a  gill  like  that  represented  in  Plate  II., 
Fig.  12,  when  placed  in  a  closed  compressor  cell,  it  is  easy  to 
determine  that  the  zone  of  autodigestion  follows  hard  upon  the 
zone  of  spore-freed  surface.  However,  it  never  invades  the  zone 
of  spore-discharge,  although  it  is  always  less  than  a  single  milli- 


THE   COPRINUS  TYPE   OF  FRUIT-BODY  205 

metre  behind  it.  The  five  zones  described,  retain  the  same 
relations  to  one  another  during  the  whole  two  days  or  so  required 
for  the  complete  discharge  of  the  spores.  They  move  upwards 
simultaneously  from  the  bottom  to  the  top  of  each  gill  (Plate  II., 
Figs.  8,  9,  and  10).  The  zone  of  spore-free  basidia,  and  the  adjacent 
portions  of  the  zones  of  spore-discharge  and  autodigestion,  can 
often  just  be  distinguished  with  the  naked  eye  upon  a  gill,  for 
together  they  give  the  appearance  of  a  very  thin  whitish  line 
next  to  the  thin  black  liquid  film  on  the  gill  edge  and  separating 
this  from  the  general  gill  surface  which,  owing  to  the  vast  number 
of  spores  borne  by  the  mature  basidia,  is  uniformly  black. 

It  is  evident  that  autodigestion  plays  a  very  important  part 
in  spore-discharge.  Its  function  is  wholly  mechanical.  It  destroys 
the  spore-freed  portions  of  the  gills  and  so  clears  them  out  of  the 
way.  Only  by  the  removal  of  these  obstacles  could  the  pileus 
gradually  turn  outwards  and  thus  cause  the  production  of  spaces 
between  the  lower  ends  of  the  gills  higher  and  higher  up  as  these 
become  shorter  and  shorter.  Such  spaces  are  absolutely  necessary 
to  permit  of  the  liberation  of  the  spores  from  the  zones  of  spore- 
discharge.  The  basidia  shoot  out  their  spores  horizontally  into 
the  spaces  between  the  gills  (Plate  III.,  Figs.  16  and  17).  The 
maximum  horizontal  distance  to  which  the  spores  travel,  before 
their  horizontal  motion  is  reduced  to  zero  by  the  resistance  of 
the  air,  is  about  0*1  mm.  After  making  the  usual  sporabolic 
curves,  the  spores  fall  vertically  downwards  with  a  steady  terminal 
velocity  of  about  4  mm.  per  second.1  Since  the  zones  of  spore- 
discharge  are  so  near  the  gill  edges,  the  spores  have  only  to  fall 
a  distance  of  about  0-5  mm.  between  two  gills  in  order  to  effect 
their  escape.  The  risk  of  the  spores  striking  the  gill  sides  is 
thereby  reduced  to  a  minimum.  As  the  spores  fall  below  the 
pileus,  doubtless  they  lose  water  rapidly.2  Their  velocity  pro- 
bably diminishes  to  about  2  mm.  per  second  in  the  course  of  a 
minute.  On  leaving  the  fruit-body,  the  spores  are  carried  off 
by  air-currents  which  scatter  them  far  and  wide.  The  discharge 
of  spores  into  the  air  takes  place  day  and  night  continuously.  It 
has  already  been  mentioned  that  a  large  fruit-body  was  found  to 
1  Chap.  XV.  *  Chap.  XVI. 


206 


RESEARCHES   ON  FUNGI 


produce  about  5,000,000,000  spores.1  Since  the  entire  discharge 
of  the  spores  from  a  large  pileus  usually  takes  about  48  hours, 
it  seems  safe  to  state  that  in  this  case  more  than  1,000,000  would 
have  been  liberated  upon  the  average  each  minute.  One  need 
not  therefore  be  surprised  at  the  rapidity  with  which  a  black 

spore  -  deposit  collects 
upon  white  paper,  Avhen 
this  is  placed  beneath  a 
fruit-body  which  has  its 
natural  orientation  under 
a  bell-jar  (Fig.  72). 

My  OA\rn  observations 
seem  to  point  conclu- 
sively to  the  fact  that 
the  spores  of  Coprinus 
comatus,  like  those  of 
the  Mushroom  and  all 
other  Agaricinese,  are  dis- 
tributed by  the  wind. 
HoAvever,  another,  and  I 
believe  quite  erroneous, 
explanation  of  this  mat- 
ter, has  found  its  Avay 
into  botanical  literature. 

FIG.  72. —The  liberation  of  spores  by  Coprinus  comatus.  Ifc    SCCIUS    to    have    been 

The  fruit-body  was  gathered  in  a  field  and  then  eiio-o-pstpd     oricrinflllv    bv 

set  in  a  vertical  position  under  a  bell-jar.     As  the  su£gesl  originally    Dy 

pileus  expanded  below,  spores  began  to  fall.    The  Fulton,2  and  IS  now  given 

black  spore-deposit  upon  the  paper  around  the  .  . 

base  of  the  stipe  was  formed   in  the  course  of  in  Various  text-books.     It 

natural  s"eS.'    Photographed  by  P"  Grafton"    *     has  been  stated  that  the 

gills  turn  into  an  inky 

mass,  that  the  fluid  so  produced  contains  the  spores,  and  that 
insects  visit  the  fruit-bodies,  lick  up  the  ink,  carry  off  the  spores, 
and  thus  spread  them  from  place  to  place.  This  seems  to  me 

•^  Chap.  V. 

2  T.  W.  Fulton,  "The  Dispersal  of  the  Spores  of  Fungi  by  the  Agency  of 
Insects,  with  special  reference  to  the  Phalloidei,"  Ann.  of  Bot.,  vol.  iil,  1889-90, 
pp.  215-216.     I  fail  to  follow  Fulton  in  finding  a  resemblance  between  the  pilei 
of  Coprini  and  the  capitula  of  Compositse. 

3  E.g.  E.  M.  Freeman,  Minnesota  Plant  Diseases,  1905,  pp.  178-179. 


THE   COPRINUS  TYPE   OF  FRUIT-BODY  207 

to  be  nothing  more  than  an  assumption  based  on  an  imperfect 
analogy  with  the  phenomena  of  spore  -  dispersion  in  Phallus 
impudicus  and  other  Phallinese.  I  have  carefully  watched  auto- 
digesting  fruit-bodies  of  Coprinus  comatus  in  the  field  and  have 
failed  to  observe  any  insects  visiting  them.  The  absence  of  any 
red  or  suggestive  colour  on  the  exterior  of  the  pileus  and  the 
scarcely  noticeable  and  inoffensive  odour,  are  additional  facts 
pointing  to  the  conclusion  that  the  fungus  has  no  special  arrange- 
ments with  insect  visitors.  The  chief  evidence  in  refuting  the 
insect  theory,  however,  is  that  the  liquid  drops  which  in  moist 
weather  hang  from  the  margin  of  the  pileus,  contain  practically 
no  spores.  The  few  which  are  present,  doubtless,  have  got  into 
them  by  accident.  It  seems  quite  certain  that  the  majority  of 
the  spores  are  always  carried  off  by  the  wind. 

Upon  gathering  "deliquescing"  fruit-bodies  of  Coprinus  comatus, 
mycologists  usually  find  it  convenient  to  lay  them  more  or  less 
horizontally  in  the  collecting  tins  in  order  to  bring  them  to  the 
laboratory.  Under  these  conditions,  in  the  course  of  an  hour  or 
so,  the  lower  ends  of  the  gills,  where  autodigestion  is  taking 
place,  become  hopelessly  stuck  together  and  the  spaces  between 
their  ends  blocked  up.  The  dark  fiuid  then  becomes  laden  with 
spores.  The  delicate  mechanism  for  securing  the  liberation  of 
spores  into  the  air  thus  becomes  entirely  spoiled.  Possibly,  the 
sight  of  the  gills  stuck  together  in  an  inky  mass  in  this  way  has 
given  rise  to  the  erroneous  impression  that  the  spores  in  nature 
become  involved  in  the  putrescent  fruit-body.  In  order  to  study 
the  phenomenon  of  spore-liberation  in  its  normal  course,  the  best 
plan  is  as  follows.  One  gathers  a  large  fruit-body  which  is  opening 
out  below  and  has  therefore  reached  a  stage  in  its  development 
just  previous  to  the  beginning  of  autodigestion.  One  lays  the 
fruit-body  in  a  vasculum  in  any  convenient  position  and,  on 
arrival  at  the  laboratory,  one  plants  it  upright  in  wet  sand  by 
means  of  its  stipe,  so  that  it  comes  to  have  the  same  orientation 
that  it  had  when  growing  in  nature.  In  the  course  of  a  few  hours 
normal  autodigestion  begins  at  the  bottom  of  each  gill  and  pro- 
gresses upwards  just  as  in  the  field.  The  spaces  between  the  ends 
of  the  gills  remain  open,  and,  if  the  fruit-body  is  covered  with  a 


208 


RESEARCHES   ON   FUNGI 


bell-jar,  the   spores   discharged   into    the   air   can   be   collected  on 

paper. 

Spore  -  deposits   can   be   collected   on    paper   from   any  of  the 

Coprini.       I    have    obtained    spores    in    this  way   not    only   from 

Coprinus  comatus 
but  also  from  C. 
atramentarius,  C. 
micaceus,  C.  fime- 
tarius,  var.  cinereus, 
as  well  as  from  a 
number  of  smaller 
species.  Duggar l 
is  therefore  in  error 
when,  in  discussing 
the  means  of  mak- 
ing pure  cultures 
of  edible  Hymeno- 
mycetes,  he  says 
"  members  of  the 
genus  Coprinus  are 
deliquescent,  and 
here  it  is  imprac- 
ticable to  procure 
spores  by  the  spore- 
print  method." 
With  the  exercise 
of  a  little  care,  one 
can  obtain  as  dense 
a  spore-deposit  from 
a  Coprinus  coma- 
tus as  from  a  Mush- 


FlG.  73. — Fruit-bodies  of  Coprinus  atramentarius  shedding 
spores.  Although  the  lower  parts  of  the  stipes  are 
oblique,  the  upper  parts  are  vertical,  so  that  the  gills 
lie  in  vertical  planes.  The  lower  parts  of  the  pilei  are 
splitting  so  as  to  permit  of  the  requisite  separation  of 
the  gills  which  are  undergoing  autodigestion.  Photo- 
graphed at  Sutton  Park,  Warwickshire,  by  J.  E.  Titley. 
Reduced  to  about  f 


Coprinus  atramentarius  (Fig.  73)  and  C.  micaceus  (Fig.  74) 
were  found  to  shed  their  spores  in  essentially  the  same  manner 
as  C.  comatus.  C.  plicatilis,  and  other  very  small  species,  behave 

1  B.  M.  Duggar,  "  The  Principles  of  Mushroom  Growing  and  Mushroom  Spawn 
Making,"  U.S.  Dep.  of  Agric.,  Bureau  of  Plant  Industry,  Bulletin  No.  85,  1905,  p.  22. 


THE   COPRINUS  TYPE   OF  FRUIT-BODY  209 

somewhat  differently.  The  gills  ripen  and  shed  their  spores  from 
below  upwards.  As  the  pileus  opens  out,  the  necessary  inter- 
lamellar  spaces  widen  from  below  upwards.  However,  the  entire 
opening  of  the  pileus,  which  eventually  becomes  disc-shaped,  is 
accomplished  without  "deliquescence."  Each  gill  splits  vertically 
from  above  and  the  two  halves  become  pulled  out  laterally.  The 
expansion  of  the  pileus  and  the  necessary  spacing  of  the  gills  is 
thus  satisfactorily  brought  about  without  autodigestion,  which 
process  in  these  tiny  fruit-bodies  would  be  superfluous. 

Massee 1  has  recently  stated  that  "  Many  species  included  in 
Coprinus  as  C.  plieatUis  and  others  having  dry,  non-deli- 
quescent gills,  have  no  real  affinity  with  this  genus."  Now 
that  the  function  of  autodigestion  has  been  discovered,  this  view 
can  no  longer  be  regarded  as  tenable.  Autodigestion  alone  is  not 
a  decisive  test  for  placing  a  species  in  the  genus  Coprinus. 
In  its  absence  in  the  smaller  species,  such  as  C.  plicatilis, 
Coprinus  characters,  e.g.  thinness  of  the  flesh,  general  structure 
and  splitting  of  the  gills,  protuberant  basidia  separated  by  para- 
physes  of  a  special  type,  and  particularly  the  ripening  and  dis- 
charge of  the  spores  in  succession  in  a  direction  proceeding  from 
the  pileus  margin  to  the  pileus  centre,  are  still  sufficiently  obvious. 
Even  in  C.  plicatiloides  (Fig.  26,  p.  70),  one  of  the  smallest  of  all 
Coprini,  where  the  expanded  parasol-like  pileus  is  often  only  5  mm. 
or  even  less  in  diameter,  the  process  of  spore-discharge  proceeds 
centripetally.  It  always  begins  first,  and  is  completed  first, 
around  the  periphery  of  the  pileus,  and  the  last  spores  to  be  set 
free  are  those  in  the  neighbourhood  of  the  stipe.  The  gradual 
progress  of  spore-discharge  is  therefore  essentially  similar  in 
the  diminutive  C.  plicatiloides  and  in  the  relatively  gigantic 
C.  comatus.  This  seems  to  me  to  be  strong  evidence  that  both 
species  have  been  rightly  placed  within  the  same  genus. 

There  can  be  little  doubt  that  some  of  the  smaller  and  more 
delicate  species  of  Coprinus  are  largely  dependent  on  the  weather 
for  success  in  liberating  their  spores  into  the  air.  In  very  dry 
weather,  especially  when  it  is  windy,  I  have  noticed  that  fruit- 
bodies  of  C.  plicatilis,  growing  on  a  lawn,  and  those  of 

1  G.  Massee,  Text-Book  of  Fungi,  London,  1906,  p.  364. 

O 


2IO 


RESEARCHES   ON  FUNGI 


Coprinus  micaceus,  shrivel  up  before  spore-discharge  has  been 
completed,  and  sometimes,  indeed,  without  its  beginning  at  all. 
Doubtless  this  is  due  to  too  rapid  transpiration  from  the  gills 
and  upper  surface  of  the  pileus.  In  moist  weather  the  gills  of 
C.  micaceus  undergo  the  typical  process  of  autodigestion,  which 
has  the  same  relation  to  the  zones  of  spore-discharge  as  in 
C.  comatus.  Stages  in  the  opening  out  of  the  pileus  and  in 


FlG.  74. — Coprinus  micaceus.  A  group  of  fruit-bodies  in  a  late  stage  of 
development.  The  gills  have  almost  disappeared  owing  to  autodigestion. 
The  rim  of  the  pileus  in  the  foreground  is  markedly  recurved.  Photo- 
graphed at  Sutton  Park,  Warwickshire,  by  J.  E.  Titley.  About  £ 
natural  size. 

the    disappearance    of    the    gills    of    C.    micaceus    are    shown    in 
Plate  III.,  Figs.  18,  19,  and  20. 

As  a  result  of  my  investigations,  I  have  come  to  recognise  two 
distinct  types  of  spore-producing  and  spore-liberating  fruit-bodies 
in  the  Agaricineae.  One  is  represented  by  the  Mushroom  and 
the  other  by  C.  comatus.  The  former  is  by  far  the  more 
common  and  includes  all  ordinary  Agaricinese,  whilst  the  latter 
is  restricted  to  the  "deliquescing"  Coprini.  The  significant 


THE   COPRINUS  TYPE   OF  FRUIT-BODY 


211 


points  of  difference  between  the  two  types  may  be  tabulated  as 
follows : — 


Xo. 

1'salliota  campestris. 

Coprinus  comstiis. 

1 

Flesh  thick. 

Flesh  very  thin  or  mem- 
branous. 

2 

Gills  more  or  less  hori- 
zontally outstretched  at 
maturity. 

Gills  more  or  less  vertically 
placed  at  maturity. 

3 

Spores  not  at  all  ripe  or 
all  discharged  simultane- 
ously on  any  part  of  a 
gill. 

Spores  all  ripen  and  are 
all  discharged  simultane- 
ously in  a  narrow  zone 
which  progresses  slowly 
from  the  base  to  the  top 
of  each  gill. 

4 

Gills  do  not  undergo  a  pro- 
cess of  autodigestion. 

Gills  become  destroyed  by 
autodigestion  from  below 
upwards. 

5 

The  stipe  has  attained  its 
full  length  before  the 
spores  are  liberated. 

The  stipe  elongates  con- 
siderably during  libera- 
tion of  the  spores. 

For  each  fruit-body  the  five  facts  are  correlated  and  only  find 
their  full  significance  in  reference  to  each  other. 

Doubtless,  within  certain  limits,  there  has  been  a  tendency  for 
the  survival  of  those  fruit-bodies  which  produce  and  successfully 
liberate  the  maximum  number  of  spores  with  the  least  expendi- 
ture of  fruit-body  substance  and  energy.  In  both  our  types  this 
desideratum  has  been  met  in  part  by  the  production  of  central 
tubular  stipes,  symmetrical  radiate  pilei,  closely  packed  basidia, 
tiny  spores,  and  a  much  folded  hymenium  situated  on  the  plate- 
like  gills.  Further  arrangements,  however,  in  the  two  types 
present  marked  differences. 

In  the  Mushroom,  adjacent  basidia  on  any  part  of  a  gill 
mature  successively  and  shed  their  spores  as  soon  as  these  are 
ripe  (cf.  Plate  I.,  Fig.  3).  Every  square  millimetre  of  hy menial 
surface  on  each  gill,  therefore,  sheds  a  certain  number  of  spores 
each  minute  throughout  the  entire  spore-liberating  period  of  the 
fruit-body.  This  necessitates  that  sufficient  space  shall  be  provided 
between  adjacent  gills  throughout  their  whole  length  by  the  time 


212  RESEARCHES   ON   FUNGI 

spore-discharge  begins.  These  spaces  are  provided  for  a  maximum 
number  of  gills  by  the  long  axes  of  the  latter  becoming  horizontally 
outstretched  at  maturity  (Plate  I.,  Fig.  2 ;  Plate  IV.,  Fig.  25).  In 
order  to  fix  the  gills  in  this  position  (with  their  planes  vertical), 
the  whole  fruit-body  must  have  the  necessary  rigidity.  This  is 
given  by  the  thick  flesh. 

In  a  fruit-body  of  Coprinus  comatus  there  is  much  more  gill- 


FlG.  75. — Amanita  muscaria.  Two  fruit-bodies  having  the  Ps/tlliota  campcstris 
type  of  spore-discharge.  The  gills  are  horizontally  outstretched.  The 
space  provided  by  the  stipe  beneath  the  pileus  allows  air-currents  to 
readily  bear  away  the  falling  spores.  In  nature  the  tops  of  the  pilei,  which 
bear  white  squamulae,  are  coloured  a  brilliant  red.  Photographed  at 
Sutton  Park,  Warwickshire,  by  J.  E.  Titley.  About  £  natural  size. 

surface  in  proportion  to  the  whole  mass  than  in  a  Mushroom. 
The  former,  therefore,  has  solved  the  problem  of  developing  the 
maximum  amount  of  spore-bearing  hymenium  with  the  least 
possible  expenditure  of  fruit-body  substance  and  energy,  much 
more  successfully  than  the  latter  (cf.  Plate  I.,  Figs.  1  and  2). 

The  Coprinus  has  such  extremely  thin  flesh  to  its  pileus  that 
it  would  be  mechanically  impossible  for  it  to  support  its  gills  at 
maturity  with  their  long  axes  in  the  horizontal  position.  Associated 


THE   COPRINUS  TYPE   OF  FRUIT-BODY  213 

with  the  extremely  reduced  flesh,  we  find  that  the  long  axes  of 
the  gills  are  almost  vertical  when  spore-liberation  begins.  This 
arrangement  reduces  the  strain  on  the  flesh  to  a  minimum.  The 
pileus  simply  presses  downwards  on  the  stipe.  When  the  gills 
have  become  vertical  at  maturity  they  are  then  closely  packed 
together  throughout  their  entire  length  except  for  their  extreme 
lower  ends,  where  the  change  of  shape  of  the  pileus  from  the 
barrel  form  to  the  bell  form  has  caused  them  to  separate.  It 
would  be  quite  impossible  for  spores  to  be  liberated  from  the 
long  vertical  gills  throughout  every  part  of  their  whole  length 
simultaneously  as  in  the  Mushroom,  for  the  gills  are  too  close 
together.  If  wide  spaces  were  provided  between  them,  not  only 
>vould  this  necessitate  a  large  reduction  in  the  number  of  the 
gills,  but  a  large  number  of  spores  would  require  to  fall  vertically 
downwards  between  the  gill-plates  a  distance  of  several  centi- 
metres. In  that  case,  unless  the  gill-planes  were  quite  vertical, 
a  considerable  proportion  of  the  spores  would  strike  the  hymenium 
on  falling,  adhere  there,  and  be  wasted.  Granted,  therefore,  that 
the  gills  are  closely  packed  and  vertically  extended  at  maturity, 
it  is  obvious  that  a  different  arrangement  for  spore-liberation  has 
to  be  adopted  to  that  found  in  the  Mushroom.  As  a  matter  of 
fact,  as  we  have  already  seen,  the  Coprinus  sheds  its  spores  from 
a  narrow  zone  of  spore- discharge  which  passes  on  each  gill  from 
below  upwards.  At  the  zones  of  spore-discharge,  the  gills  are 
always  sufficiently  far  apart  (about  0*2  mm.)  to  permit  of  the 
spores,  when  violently  projected  from  their  sterigmata,  describing 
the  usual  sporabolic  paths  unhindered.  To  enable  the  gills  to 
move  apart  from  one  another  higher  and  higher  up  as  the  zones 
of  spore-discharge  ascend  upon  them,  the  process  of  autodigestion 
comes  into  play.  This  causes  the  removal  of  the  spore-freed 
portions  of  the  gills  and  thus  allows  the  fruit-body  to  gradually 
open  out  and  thereby  separate  the  gills  higher  and  higher  up. 
Without  autodigestion  it  would  be  difficult  to  imagine  how  the 
necessary  interlamellar  spaces  could  be  provided  at  the  moving 
zones  of  spore-discharge.  Toward  the  end  of  the  period  of  spore- 
discharge,  the  much  shortened  gills  become  horizontally  out- 
stretched like  those  of  a  Mushroom.  At  this  stage,  the  pileus 


2i4  RESEARCHES   ON  FUNGI 

requires  to  be  disc-shaped  in  order  to  permit  the  parts  of  the 
gills  nearest  the  stipe  to  obtain  the  requisite  spaces  for  spore- 
discharge  between  them.  The  very  thin  flesh  is  also  now  quite 
sufficient  to  support  the  much  reduced  burden  of  the  gills  in  the 
horizontal  position. 

During  the  process  of  spore-discharge,  the  stipe  of  Coprinus 
comatus  elongates  considerably.  It  adds  a  number  of  centimetres 
to  its  length  and  often  becomes  a  foot  long  (Plate  IV.,  Fig.  22). 
As  the  fluid  produced  during  autodigestion  is  gradually  lost  by 
evaporation  and  dripping,  the  weight  of  the  pileus,  i.e.  the  load 
which  the  stipe  has  to  support,  undergoes  progressive  reduction. 
The  higher  the  pileus  can  be  raised  with  mechanical  safety,  the 
better  will  be  the  chance  of  the  spores  escaping  obstacles  and 
being  carried  off  by  the  wind.  It  seems  clear  that  the  gradual 
raising  of  the  pileus  by  the  elongation  of  the  stipe  is  correlated 
with  the  progressive  diminution  of  the  pileus  weight.  In  the 
Mushroom,  on  the  other  hand,  the  burden  to  be  borne  by  the 
stipe  does  not  alter  during  spore-liberation.  In  keeping  with  this 
we  find  that  in  this  type  of  fruit-body  the  stipe  attains  its 
maximum  length  before  spore-discharge  begins. 

If  the  Coprinus  and  the  Mushroom  types  be  compared,  I 
think  it  must  be  admitted  that  the  former  is  superior  to  the 
latter  in  producing  the  maximum  number  of  spores  with  the 
minimum  of  fruit-body  substance  and  energy.  A  Coprinus  fruit- 
body  with  its  extreme  reduction  of  flesh,  vertical  position  of  the 
gills,  successive  ripening  of  the  spores  from  below  upwards,  and  its 
beautifully  regulated  autodigestion,  may  be  thought  of  as  having 
been  evolved  from  a  more  generalised  fruit-body  of  the  Mushroom 
type,  with  thick  flesh,  horizontal  gills,  irregular  ripening  of  the 
basidia,  and  absence  of  autodigestion.  The  special  features  of  a 
typical  Coprinus  fruit-body  are  bound  up  with  its  umbrella  shape. 
It  seems  to  me  that  only  after  this  had  been  attained  could  the 
special  Coprinus  arrangements  have  been  developed  and  become 
effective.  For  this  reason  I  regard  the  genus  Coprinus  as  having 
been  derived  entirely  from  a  fungus  having  fruit-bodies  of  the 
Mushroom  type  with  central  stipe  and  a  symmetrically-placed, 
gill-bearing  pileus.  At  the  present  day  there  are  no  Coprini  with 


THE   COPRINUS  TYPE   OF  FRUIT-BODY  215 

dimidiate  form  corresponding  to  Lenzites,  &c.  In  my  opinion  the 
explanation  of  this  fact  is  not  that  such  fruit-bodies  have  become 
extinct  but  that  they  never  existed. 

Massee  in  his  "Revision  of  the  Genus  Coprinus"  states  that 
"  the  species  of  Coprinus  differ  from  the  remainder  of  the  Agari- 
cinefe  in  one  important  biological  feature — the  deliquescence  of 
the  gills  at  maturity  into  a  liquid  which  drops  to  the  ground, 
carrying  the  mature  spores  along  with  it."  This  mode  of  spore- 
dissemination  he  describes  as  "primitive  and  relatively  imperfect," 
"  as  compared  with  the  minute  wind-borne  spores  of  the  remainder 
of  the  Agaricineae."  *  Massee  takes  this  mode  of  spore-dissemina- 
tion as  important  evidence  that  "in  the  genus  Coprinus  we  have 
in  reality  thg  remnant  of  a  primitive  group  from  which  have 
descended  the  entire  group  of  Agaricine*  having  wind-borne 
spores."  Since  my  own  investigations  have  now  shown  that  the 
spores  of  the  Coprini  are  wind-borne,  it  must  be  concluded  that 
Massee's  argument  for  the  ancestral  position  of  the  Coprini  is 
based  on  an  unfortunate  misconception  of  the  ecology  of  Coprinus 
fruit-bodies.  The  arrangement  for  liberating  spores  into  the  air 
by  means  of  "  deliquescence,"  instead  of  being  primitive,  appears 
to  be  the  most  highly  specialised  in  the  whole  group  of  Agaricineae. 
The  relative  antiquity  of  the  genus  Coprinus  seems  to  me  to  be 
no  easy  matter  to  decide.  However,  at  present  I  fail  to  find  any 
satisfactory  evidence  that  the  genus  is  to  be  regarded  as  closely 
related  to  the  one  from  which  the  other  groups  of  gilled  Agarics 
have  arisen.  It  seems  more  reasonable  to  regard  it  as  a  specialised 
offshoot  from  a  more  generalised  fungus  of  the  Mushroom  type. 

1  G.  Massee,  "A  Revision  of  the  Genus  Coprinus,"  Ann.  of  Bot.,  vol.  x.  p.  129  ; 
also  Text-Book  of  Fungi,  London,  1906,  p.  364. 


CHAPTER   XX 


THE   DISPERSION   OF   THE   SPORES  AFTER  LIBERATION   FROM 
THE   FRUIT-BODIES— FALCK'S  THEORY 

WE  have  now  gained  some  insight  into  the  arrangements  whereby 
spores  are  enabled  to  escape  from  hymenomycetous  fruit-bodies. 
It  still  remains,  however,  to  discuss  the  dispersion  of  the  spores 
in  the  outer  air.  Doubtless,  in  the  narrow,  blindly-ending  tubes 
of  the  Polyporese,  and  between  the  closely-packed  gills  of  the 
Agaricinese,  the  air  is  extremely  still,  so  that  the  spores  fall 
approximately  vertically  downwards  in  it,  in  the  manner  already 
discussed  in  Chapter  XVII.  If  the  air  between  the  pilei  and  the 
ground  were  also  quite  still,  the  spores  would  continue  falling  in 
their  vertical  paths  after  emerging  from  the  fruit-bodies,  and 
would  strike  the  ground  immediately  below  the  basidia  from  which 
they  had  been  liberated.  It  is  of  interest  to  calculate  the  length 
of  time  that  would  be  required  for  the  spores  to  reach  the  ground 
in  still  air.  The  results  of  a  few  such  calculations,  together  with 
the  data  on  which  they  are  based,  are  given  in  the  following 
Table  :— 


Approximate  Length 

Species. 

Length  of  Stipe 
between  the  B  ise  of 
the  Gills  and  the 

Approximate 
Average  Velocity 
of  Fall  of  the 

of  Time  required  for 
the  Spores  to  Fall 
from  the  Base  of  the 

Ground. 

Spores,  i 

Gills  to  the  Ground  in 

Still  Air. 

Collybia  dryophila  .     . 
Psalliota  campestris    . 

4.  cm. 
6  cm. 

0'4  mm.  per  sec. 
1'2  mm.  per  sec. 

1  min.  40  sees. 
50  seconds 

Amanitopsis  vaginata 

7*5  cm.             3  mm.  per  sec.          25  seconds 

Coprinus  comatus  .     . 

6-20  cm.            3  mm.  per  sec.       j  ^J^'1  min'  6 

(  Pileus  growing  "i 

from  a  tree 

Polyporus  squamosus 

-j  trunk  4  metres  •    1  mm.  per  sec.     !     1  hour  6  mins. 

above  the 

1        ground        J 

Estimated  from  the  data  given  in  Chaps.  XV.  and  XVI. 


THE   DISPERSION   OF  THE   SPORES  217 

It  is  clear,  from  the  results  just  given  and  from  our  knowledge 
of  the  size  of  spores  in  Hymenoinycetes  generally,1  that  for  the 
fruit-bodies  of  many  species  about  a  minute  would  be  required  for 
the  spores  to  fall  from  the  gills  to  the  ground.  Even  in  the  case 
of  Amanitopsis  vaginata,  where  the  spores  are  unusually  large  in 
addition  to  being  spherical,  about  half  a  minute  would  be  necessary. 
For  fruit-bodies  of  Polyporus,  Polystictus,  Fomes,  Stereum,  Corticiurn, 
&c.,  growing  on  tree-trunks  or  dead  branches  some  metres  high,  the 
ground  would  only  be  reached  after  the  spores  had  been  falling 
through  the  air  for  a  period  of  time  of  the  order  of  an  hour. 

It  seems  certain  that,  owing  to  the  alternation  of  day  and 
night  and  other  meteorological  causes,  the  air  above  the  surface 
of  the  earth  is  never  quite  still.  The  average  speed  of  the  air  in 
exposed  situations  is  very  considerable,  amounting  to  miles  an  hour. 
In  woods  and  meadows,  &c.,  where  ground-fungi  grow,  the  air- 
movements  are  probably  never  less  than  some  feet  per  minute, 
and,  as  every  one  knows  by  experience,  they  are  very  frequently 
much  greater.  Even  when  the  air  seems  extremely  still,  so  that 
one  cannot  feel  its  motion  and  scarcely  a  leaf  trembles  on  the 
tallest  trees,  it  is  astonishing  how  complex  and  active  are  the 
small  convection  currents  and  air-drifts  that  one  may  discover 
near  the  ground,  in  gardens  and  woods,  by  the  cautious  liberation 
of  smoke  or  puff-ball  dust.  From  what  we  know  by  experience 
of  air-movements,  and  from  the  calculations  of  the  time  that 
would  be  required  for  spores  to  fall  from  their  pilei  to  the  ground 
in  perfectly  still  air,  it  seems  to  me  to  be  an  obvious  conclusion 
that  the  external  air-currents,  as  a  rule,  are  fully  sufficient  to 
carry  off  the  falling  spores  from  beneath  the  pilei  and  to  scatter 
them  broadcast.  As  a  matter  of  fact  in  nature,  unless  a  fruit-body 
is  confined  by  dense  grass,  loose  leaves,  or  other  natural  obstacles, 
one  never  finds  any  noticeable  spore-deposit  on  the  ground  beneath 
a  pileus.  For  fruit-bodies  of  Stropharia  semiglobata,  Anellaria 
separata,  Coprinus  comatus,  or  any  other  species  growing  in  open 
pastures,  &c.,  it  seems  theoretically  impossible  that,  if  the  wind  is 
blowing  appreciably,  any  of  the  spores  should  settle  on  the  ground 
immediately  beneath  the  pilei. 

1  Chap.  XIV. 


218 


RESEARCHES   ON   FUNGI 


One  of  the  chief  functions  of  the  stipe  is  undoubtedly  to  provide 
a  space  usually  one  or  more  inches  high  between  the  under  surface 
of  the  pileus  and  the  substratum  on  which  the  fruit-body  may  grow. 
Owing  to  the  very  small  rate  of  fall  of  the  spores  and  the  relatively 
very  much  greater  average  horizontal  speed  of  air-currents  near  the 
ground,  the  space  is  amply  sufficient,  under  normal  conditions,  to 
permit  of  the  falling  spores  being  carried  away  from  the  fruit-body 
and  deposited  at  a  distance  from  it. 

Richard  Falck1  has  put  forward  the  theory  that  the  fruit-bodies 


FIG.  7<i. — Semidiagrammatic  sketch  of  a  section  in  a  field  illustrating  the  manner  in 
which  the  spores  of  the  Horse  Mushroom  (Psalliota  arvensis)  are  liberated  and 
dispersed.  A  slight  lateral  movement  of  the  air  is  supposed  to  be  carrying  the 
spore-cloud  away  from  the  underside  of  the  pileus.  Reduced  to  £. 

are  themselves  specially  adapted  to  produce  air-currents  for  the 
purpose  of  scattering  the  spores.  His  theory  is  founded  on  the  fact 
that  fruit-bodies,  when  insulated,  become  distinctly  warmer  than  the 
surrounding  atmosphere.  In  one  of  his  experiments,  he  found  that 
the  hy menial  tubes  of  Polyporus  squamosus,  placed  thickly  together 
in  a  carefully  insulated  chamber  for  ten  hours,  became  9-6°  C. 
warmer  than  similarly  situated  hymenial  tubes  which  had  previously 

1  "  Die  Sporenverbreitung  bei  den  Basidiomyceten  und  der  biologische  Wert 
der  Basidie,"  Beitriige  zur  Biologie  der  Pflanzen,  Bd.  IX.,  1904,  p.  1. 


FALCK'S  THEORY  219 

been  killed  by  heating.  Falck  believes  that  "  the  fruit-bodies  pro- 
duce heat  not  to  raise  their  own  temperature  but  to  warm  the  layers 
of  air  beneath  the  pilei."  l  He  considers  that  the  heat  thus  given  off 
creates  convection  currents  in  which  the  spores  are  borne  away  from 
the  pilei.  In  support  of  this,  Falck  has  described  experiments  in 
which  spore-deposits  were  obtained  from  pilei  which  had  been 
suspended  in  closed  glass  vessels.  He  found  that  the  spores  were 
carried  up  and  down  in  the  glass  vessels  so  that  they  settled  upon 
ledges  placed  both  above  and  below  the  pilei.  Falck  has  followed 
out  his  idea  still  further.  After  showing  that  the  presence  of 
maggots  leads  to  an  appreciable  increase  in  the  temperature  of 
insulated  pilei.  he  came  to  the  following  theoretical  conclusions. 
Tlje  pileus  flesh  of  large  Agarics  has  become  specially  thickened  and 
laden  with  food  substances  for  the  purpose  of  feeding  maggots.  The 
maggots  respire  actively  and  thus  produce  heat,  which  is  added  to 
that  resulting  from  the  respiration  of  the  pileus,  and  is  made  use  of 
for  increasing  the  convection  currents  which  bear  away  the  spores 
in  the  neighbourhood  of  the  gills.  We  thus  have  a  symbiotic 
relationship  between  hymenomycetous  fruit-bodies  and  flies. 

It  must  be  admitted  that  Falck's  theory  is  a  very  ingenious  one. 
However,  I  am  not  sure  to  what  extent  we  are  justified  in  drawing 
conclusions  from  the  laboratory  experiments  as  to  what  actually 
happens  in  fields  and  woods.  Proof  has  yet  to  be  brought  forward 
that  in  nature  the  pilei  become  sufficiently  warmed  to  produce 
effective  convection  currents.  If  the  ordinary  air-currents  in  fields 
and  woods  are  never  less  than  a  few  feet  per  minute,  and  are  usually 
much  greater,  it  seems  to  me  that  they  must  be  so  active  in  carrying 
away  the  spores  from  the  fruit-bodies  that  the  convection  currents 
arising  from  the  very  slightly  warmed  condition  of  the  pilei  can  be 
only  quite  insignificant,  and  therefore  ineffective,  in  comparison. 
From  this  consideration  it  seems  that  in  nature  the  heat  produced 
by  a  pileus  must  be  generally  useless  and  unnecessary  for  the  purpose 
assigned  to  it  by  Falck. 

When  the  wind  is  blowing,  transpiration  becomes  active.  Pos- 
sibly the  loss  of  heat  from  a  fruit-body  thereby  occasioned,  counter- 
balances the  gain  by  respiration.  Falck's  theory  would  be  placed  on 
1  Loc.  cit.,  p.  32. 


220  RESEARCHES   ON  FUNGI 

a  much  firmer  basis  if  it  could  be  shown  that  out  in  the  open  the 
temperature  of  fruit-bodies  becomes  appreciably  higher  than  that  of 
the  surrounding  atmosphere,  but  this  has  not  yet  been  done.  For 
Polyporus  squamosus  (Fig.  1)  and  other  fruit-bodies  growing  on 
trees,  where  air-currents  are  never  absent  and  the  free  space  below 
the  pilei  is  usually  great,  for  small  or  thin  fruit-bodies  such  as  those 
of  Mycena,  Galera,  Schizophyllum,  Corticium,  Stereum,  and  Poly- 
stictus,  and  also  quite  generally  for  all  fruit-bodies  during  weather 
which  is  at  all  windy,  the  unimportance  of  any  very  slight  warming 
of  the  pilei  seems  to  me  to  be  obvious. 

As  a  rule,  in  nature,  it  is  impossible  to  see  what  happens  to 
spores  on  leaving  the  pileus.  Otherwise  a  direct  test  might  quickly 
be  applied  to  Falck's  theory.  However,  in  the  case  of  Polyporus 
squamosus,  as  described  in  Chapter  VI.,  I  have  been  able  to  see  the 
spore-clouds  leaving  a  large  fruit-body  growing  on  a  log.  The  log 
was  placed  in  a  closed  greenhouse,  where  the  air  was  so  quiet  that 
one  could  not  feel  that  it  was  moving.  As  the  spores  emerged  from 
the  hymenial  tubes,  they  were  carried  along  the  underside  of  the 
pileus  in  one  direction  by  a  very  slow  air-current  moving  at  the  rate 
of  a  few  feet  per  minute.  The  spore-clouds  could  be  seen  to  drift 
laterally  to  a  distance  of  2  metres  from  the  fruit-body.  Whilst 
doing  so,  they  were  gradually  broken  up  by  small  but  very  complex 
convection  currents,  the  presence  of  which  was  only  revealed  by  the 
spore-movements.  As  the  spore-cloud  moved  outwards  from  the 
edge  of  the  pileus,  it  showed  no  tendency  to  pass  upwards.  In  the 
course  of  several  hours,  nothing  happened  to  suggest  that  the  fruit- 
body  was  giving  off  so  much  heat  that  it  produced  convection 
currents  of  importance  in  scattering  the  spores.  It  seems  to  me  that 
these  observations  are  distinctly  adverse  to  Falck's  theory,  for  they 
not  only  show  that,  even  when  the  air  seems  very  still,  quite  slow 
air-currents  due  to  external  causes  are  of  the  greatest  importance 
in  carrying  the  spores  from  beneath  a  pileus,  but  also  that  the  con- 
vection currents  produced  by  a  large  pileus  may  be  practically 
inappreciable  when  this  is  not  insulated. 

However,  it  might  be  argued  that  the  fruit-body  was  a  solitary 
one ;  that  Polyporus  squamosus  frequently  produces  from  four  to  ten 
sporophores  in  a  densely  imbricated  cluster ;  that  the  space  between 


FALCK'S   THEORY  221 

any  two  would  become  slightly  warmed,  and  that,  in  consequence, 
useful  convection  currents  would  be  formed.  However,  since  the 
fruit-bodies  are  developed  at  some  height  on  trees  (cf.  Fig.  1),  any 
such  convection  currents  would  most  probably  always  be  swamped 
by  more  pronounced  air-movements.  If  it  be  granted  that  there 
is  no  special  adaptation  for  producing  heat  in  the  fruit-bodies  of 
Polyporus  squamosus,  then  the  adaptation  part  of  Falck's  theory 
becomes  much  weakened,  for  it  was  with  this  species  that  one  of 
the  highest  rises  in  temperature  was  obtained  in  the  insulation 
experiments. 

The  maggots  which  so  frequently  are  to  be  found  in  fruit-bodies, 
in  most  instances  at  least,  seem  to  me  to  be  in  no  way  beneficent 
to,  the  latter,  and,  in  general,  I  am  strongly  inclined  to  look  upon 
them  simply  as  harmful  parasites.  It  would  need  a  special  investi- 
gation to  decide  the  matter,  but  it  seems  probable  that  of  two 
fruit-bodies  equal  in  size,  but  one  of  them  free  from  maggots  and 
the  other  badly  infected,  the  former  would  produce  and  liberate  the 
greater  number  of  spores.  Even  if  they  both  liberated  the  same 
number,  we  could  still  regard  the  maggots  in  the  same  light  as  some 
gall-insects,  i.e.  as  parasites  which,  as  a  rule,  do  no  very  appreciable 
amount  of  harm,  and  for  getting  rid  of  which  the  plants  concerned 
possess  no  mechanism.  Sometimes  the  harm  done  is  quite  obvious. 
In  a  number  of  instances  in  the  field,  I  have  noticed  fruit-bodies  of 
Amanita  rubescens,  &c.,  with  the  gills  perforated  and  otherwise 
damaged  by  maggots  long  before  the  spores  had  all  been  shed. 
Occasionally,  at  an  equally  early  period,  the  flesh  of  a  pileus  becomes 
so  weakened  by  the  inroads  of  these  animals  that  it  can  no  longer 
support  the  gills  in  the  requisite  vertical  planes. 

Doubtless,  the  heat  which  an  expanding,  maggot-free  pileus 
produces,  like  that  arising  in  the  rapidly  opening  capitula  of  Com- 
positae,  is  due  to  respiration  accompanying  other  active  metabolic 
changes.  The  gills  in  particular,  whilst  developing  and  setting  free 
their  millions  of  spores,  have  a  large  amount  of  work  to  do.  There 
seems  no  reason  to  suppose  that  the  fruit-bodies  give  rise  to  any  more 
heat  than  is  necessitated  by  the  processes  concerned  in  rapid  growth. 
Probably  puff-balls,  which  certainly  do  not  use  any  heat  which  they 
develop  for  scattering  their  spores,  would  become  warmed  on  insula- 


222  RESEARCHES   ON  FUNGI 

tion  in  the  same  manner  as  the  hymenomycetous  fruit-bodies  in 
Falck's  experiments.  The  metabolism  which  leads  to  the  production 
of  a  billion  or  more  spores  in  a  Giant  Puff-ball  in  the  course  of  a  few 
days,  must  be  very  considerable.  For  the  present,  at  least,  I  am  not 
inclined  to  look  upon  the  heat  arising  in  the  pilei  as  in  any  way 
surprising  in  amount  or  as  being  more  than  incidental  in  character. 

Although  Falck's  theory  seems  to  me  to  require  some  modifica- 
tion, and  in  any  case  to  be  of  limited  application,  its  promulgation 
has  certainly  raised  an  important  question.  The  fruit-bodies  of 
certain  species  of  Boletus,  Amanita,  Paxillus,  &c.,  have  broad  pilei 
and  comparatively  short  stipes;  and  they  often  come  up,  half 
concealed  in  grass  or  loose  leaves,  in  hollows,  dense  woods,  or  other 
protected  places.  Here  the  air,  immediately  beneath  the  gills,  on 
quiet  days  must  be  at  its  stillest.  We  require  to  know  whether 
under  such  circumstances,  owing  to  physical  or  metabolic  changes 
going  on  in  the  fruit-bodies,  convection  currents  arise  from  the 
latter  capable  of  carrying  the  spores  between  the  surrounding 
obstacles  and  lifting  them  to  such  height  that  they  pass  into  more 
active  air-currents  in  motion  above  the  herbage  or  forest  floor. 
This  ought  to  be  determined  by  direct  observation  in  nature. 
Should  such  convection  currents  be  discovered,  it  would  then  be 
necessary  to  find  out  to  what  extent  they  were  brought  about  by 
radiation,  transpiration,  or  the  giving  off  of  heat  due  to  respiration. 
If  the  air  surrounding  a  fruit-body  were  ever  quite  still,  any  con- 
vection currents  arising  from  the  pileus,  in  order  to  raise  the  spores 
above  the  pileus,  would  require  to  have  an  average  upward  velocity 
of  1-6  mm.  per  second  according  to  the  size  of  the  spores. 

Beam-of-light  and  other  observations  of  my  own  have  served 
to  corroborate  Falck's  discovery,  that  exceedingly  faint  convection 
currents,  such  as  one  can  never  feel,  are  capable  of  transporting 
the  spores  of  Hymenoinycetes  with  astonishing  ease.  Even  in 
large  closed  beakers  it  is  exceedingly  difficult  to  reduce  the  air 
to  anything  like  real  stillness.  Small  convection  currents  can 
certainly  be  produced  with  a  very  small  expenditure  of  energy. 
Whether  sufficient  can  be  given  off  by  a  large  fruit-body  to  be  of 
use  under  special  circumstances  remains  to  be  determined.  If 
this  should  prove  to  be  the  case,  we  could  draw  the  conclusion 


FALCK'S  THEORY  223 

that  millions  and  millions  of  spores,  which  otherwise  might  never 
be  dispersed,  are  as  a  matter  of  fact  spread  far  and  wide  over  fields 
and  woods. 

If  effective  convection  currents  were  given  off  by  fruit-bodies, 
then,  doubtless,  they  might  be  increased  by  the  presence  of  maggots 
in  the  pileus  and  stipe.  From  this  point  of  view  the  presence  of 
these  animals  in  the  sporophores  of  Amanita  rubescens,  &c.,  might 
be  of  occasional  advantage ;  but  it  seems  to  me  that,  from  the 
data  at  our  disposal,  we  are  not  yet  justified  in  assuming  a  symbiotic 
relationship  between  flies  and  Agarics. 

We  have  now  seen  how  easily  the  spores  may  be  conveyed  away 
from  the  fruit-bodies  by  air-currents.  The  wind,  when  travelling 
several  miles  an  hour,  must  frequently  carry  the  spores  from  a 
fruit-body  for  very  long  distances.  Owing,  however,  to  their  steady 
fall  at  the  rate  of  0*5-5  mm.  per  second,  sooner  or  later  all  spores 
must  reach  the  earth.  The  larger  the  spores,  the  sooner  will 
they  settle.  The  big  spores  of  many  species  of  Coprinus  will  not 
be  carried  on  the  average  so  far  as  the  smaller  spores  of  the  Mush- 
room or  of  Collybia  dryophila.  With  the  ultimate  fate  of  the 
spores  after  they  have  once  settled  we  are  not  here  concerned. 


CHAPTER    XXI 

THE   DISPERSION   OF   SPOKES   BY   ANIMALS— COPROPHILOUS 
HYMENOMYCETES— SLUGS   AND    HYMENOMYCETES 

THE  fruit-bodies  of  the  Hymenomycetes,  as  we  have  seen,  exhibit  many 
beautiful  arrangements  both  in  structure  and  function,  which  enable 
the  spores  to  be  liberated  into  the  air  beneath  the  hymenium  in 
such  a  manner  that  they  may  be  carried  away  by  the  wind.  A 
comparative  study  of  fruit-body  organography  in  the  numerous 
and  diverse  species  existing  at  the  present  day,  permits  us  to 
conclude  with  some  certainty  that  the  fruit-bodies  of  the  Hymeno- 
inycetes,  at  the  beginning  of  their  phylogenetic  development,  were 
anemophilous,  and  that  they  remained  so  ever  since.  However,  for 
certain  of  the  coprophilous  fungi,  or  possibly  for  most  of  them, 
animal  agency  is  made  of  secondary  use  in  bringing  the  spores 
into  a  suitable  situation  for  germination  and  further  development. 

Coprophilous  Hymenomycetes. — Certain  species  belonging  to  the 
genera  Coprinus,  Panaeolus,  Anellaria,  and  Galera  are  to  be  seen  with 
remarkable  frequency  upon  the  dung  of  horses  and  cattle,  and  one 
may  look  for  them  in  vain  upon  any  other  substrata.  It  seems 
clear  that  they  have  become  specialised  for  a  coprophilous  habit 
of  life.1  The  infection  of  the  faeces  may  take  place  in  two  ways : 
(1)  By  spores  carried  to  them  directly  by  the  wind,  and  (2)  by 
spores  which  are  first  dispersed  by  the  wind,  which  then  settle, 
and  which  are  subsequently  swallowed  with  herbage  by  the  animals 
concerned.  That  the  first  mode  of  infection  is  possible  may  be 

1  Saccardo  gives  757  species  included  in  187  genera  as  being  coprophilous. 
To  this  large  number  the  Hymenomycetes  contribute  but  few  species  as  compared 
with  the  Ascomycetes  and  Phycomycetes.  Many  coprophilous  fungi,  so  far  as  is 
known,  are  only  found  on  dung.  Species  to  the  number  of  708  are  recorded  as 
living  on  the  dung  of  Herbivora,  45  on  that  of  Carnivora,  and  4  on  that  of 
Reptilia.  Saccardo,  Sylloge  Fungorum,  XH.,  Pars.  I.,  3,  873-902.  Cited  from 
Massee  and  Salmon,  Ann.  of  Bot.,  vol.  xv.,  1901,  pp.  317,  322. 

224 


COPROPHILOUS   HYMENOMYCETES  225 

deduced  from  the  fact  that  in  the  laboratory  sterilised  horse  dung 
can  readily  be  infected  with  spores  of  various  species  of  Coprinus  : 
the  mycelium  produced  gives  rise  to  fruit-bodies  in  the  course  of 
a  few  weeks.  In  many  cases  at  least,  it  is  not  necessary  for  the 
spores  to  have  passed  through  the  alimentary  canal  of  one  of  the 
Herbivora  in  order  to  become  capable  of  development.  The  second 
mode  of  infection,  in  which  the  agency  of  the  wind  is  supplemented 
by  that  of  animals,  has  been  carefully  investigated  by  several 
observers.  Thus  Massee  and  Salmon,  using  antiseptic  methods, 
extracted  the  fsecal  matter  from  the  intestines  of  dead  rabbits  and 
found  that,  when  it  was  protected  from  aerial  infection,  there 
developed  upon  it  a  considerable  number  of  species  of  fungi,  a 
long  list  of  which  are  recorded  in  their  "Researches  on  Copro- 
philous  Fungi."1  However,  these  authors  were  not  successful  in 
obtaining  any  species  of  Hymenomycetes  in  this  way ;  but  from 
their  observations  it  seems  probable  that  the  more  frequent  mode 
of  infection  of  the  dung  of  horses  and  cattle  in  nature  is  indirect. 
The  spores  are  scattered  broadcast  over  pastures  by  the  wind :  they 
are  then  swallowed  with  grass  by  animals;  they  pass  uninjured 
through  the  alimentary  canal,  find  their  way  into  the  fsecal  matter 
as  soon  as  it  is  formed,  and  germinate  in  it  immediately  after  it  has 
been  deposited.  By  this  means  the  spores  come  to  be  intimately 
mixed  throughout  a  faecal  mass,  so  that  its  infection  is  much  more 
thorough  and  takes  place  sooner  than  could  be  the  case  with  spores 
merely  settling  upon  its  outer  surface.  No  doubt,  of  the  two  modes 
of  infection  the  more  highly  specialised  leads  to  a  more  rapid 
development  of  new  fruit-bodies. 

Coprophilous  Hymenomycetes,  such  as  many  Coprini,  are 
adapted  to  their  environment  in  three  special  ways :  firstly,  in  the 
capacity  of  the  mycelium  to  use  the  materials  contained  in  dung 
as  food  and  to  flourish  when  developing  in  faeces ;  secondly,  in 
the  spores  being  able  to  pass  through  the  alimentary  canal  of 
herbivorous  animals  uninjured ;  and,  thirdly,  in  the  nature  of  the 
fruit-bodies.  The  food  specialisation  has  advanced  so  far  that 
a  number  of  species  of  Coprinus,  &c.,  judging  from  their  distribution 

1  Massee  and  Salmon,  Ann.  of  Bot.,  vol.  xv.,  1901 ;  vol.  xvi.,  1902. 

P 


226  RESEARCHES   ON   FUNGI 

in  nature,  are  dependent  on  the  existence  of  particular  herbivorous 
vertebrates.  It  seems  likely  that  the  extinction  of  large  Herbivora 
in  past  geological  ages  has  often  brought  about  the  extinction  of 
some  of  their  associated  fungi.  With  regard  to  the  fruit-bodies 
it  may  be  pointed  out  that,  as  in  Coprinus  niveus,  Panwolus 
phalxnarum,  Anellaria  separata,  and  Galera  tenera  (cf.  Figs.  25, 
p.  68,  and  32,  p.  80),  they  usually  have  more  or  less  campanulate 
pilei  situated  on  long  and  slender  stipes.  The  latter,  at  least  in 
many  Coprini  and  probably  in  the  other  coprophilous  genera,  are 
at  first  heliotropic.  This  enables  the  compact  young  pilei  to  be 
pushed  out  into  the  open  from  beneath  or  between  balls  of  horse 
dung,  &c.,  so  that  afterwards,  when  the  stipes  change  their 
physiological  properties  and  become  negatively  geotropic  instead 
of  heliotropic,  the  pilei  are  placed  in  such  a  position  that  they 
can  expand  and  shed  their  spores  into  the  air  free  from  all  obstacles. 
The  length  and  relative  slenderness  of  a  stipe  are  well  suited  to 
enable  that  structure  to  thread  its  way  outwards  to  the  light  by 
a  process  of  growth,  and  afterwards  to  make  a  geotropic  curvature 
by  which  the  pileus  can  be  brought  into  an  advantageous  position 
for  shedding  its  spores. 

Slugs  and  Hymenomycetes. — Many  slugs  find  certain  fruit- 
bodies  exceedingly  palatable  and  often  devastate  them  in  a  wood 
to  a  surprising  extent.  One  sometimes  has  difficulty  in  obtaining 
a  single  intact  specimen  of  Russula  emetica,  R.  citrina,  Amanita 
muscaria,  &c.,  even  where  they  occur  in  considerable  numbers. 
The  gills  are  particularly  relished,  but  large  pieces  of  the  pileus 
flesh  are  also  frequently  devoured. 

Voglino1  has  made  an  investigation  upon  the  relations  exist- 
ing between  slugs  and  Hymenomycetes,  and  has  arrived  at  a 
very  interesting  conclusion.  His  chief  observations  were  as  follows. 
The  digestive  tracts  of  slugs  collected  in  some  pine  woods  were 
found  to  contain  germinating  spores  of  the  following  species: 
Tricholoma  humile,  Mycena  alkalina,  Inocybe  fastigiata,  Lactarius 
deliciosus,  and  species  of  Russula.  Slugs  were  fed  with  fruit-bodies 
of  Russulse  and  Lactarii,  and  subsequently  numerous  germinating 

1  P.  Voglino,  "Richerche  intorno  all'  azione  delle  lumache  e  dei  rospi  nello 
sviluppo  di  Agaricini,"  Nuovo  Giornale  Botanico,  vol.  27,  1895,  pp.  181-185. 


SLUGS   AND   HYMENOMYCETES  227 

spores  of  the  species  used  were  found  in  the  digestive  tracts  of 
the  slugs  and  also  in  their  faeces.  When  the  faeces  were  placed 
in  hanging  drops,  the  germ-tubes  developed  into  a  branched 
mycelium.  The  spores  of  certain  Hymenomycetes  refused  to 
germinate  in  ordinary  culture  media,  but  germinated  readily  in 
the  fluid  obtained  from  the  digestive  tract  of  a  slug.  An  enclosure 
was  made  around  some  ten  specimens  of  Hebeloma  fastibile  which 
were  growing  in  the  open,  and  four  starved  slugs  were  introduced 
into  it.  In  a  few  days  the  lamellae  of  all  the  fruit-bodies  were 
completely  devoured.  One  of  the  slugs  when  dissected  was  found 
to  contain  germinating  spores  of  the  fungus  in  its  digestive  tract. 
The  enclosure  was  kept  moist  with  sterilised  water  and  maintained 
for  about  a  year.  At  the  end  of  this  period  it  was  observed  that 
the  specimens  of  Hebeloma  fastibile  were  much  more  numerous 
in  the  enclosure  than  elsewhere  in  the  neighbourhood.  Toads 
which  were  collected  in  some  pinewoods  were  found  to  contain 
germinating  spores  of  species  of  Russula  and  Lactarius  within 
their  alimentary  canals.  Some  toads  which  were  fed  with  slugs 
were  subsequently  found  to  contain  spores  of  Russula  in  an  advanced 
state  of  germination.  Voglino  came  to  the  conclusion  that  the 
propagation  of  fleshy  Agarics,  especially  of  Russulse  and  Lactarii, 
is  in  a  large  measure  due  to  slugs  and  toads  which  provide  con- 
ditions in  their  digestive  tracts  for  spore  germination. 

Although  it  may  be  true  that  slugs  help  in  the  local  dispersal 
of  spores  in  a  wood  or  field  and  provide  conditions  for  their 
germination,  these  animals,  owing  to  their  slow  rate  of  movement, 
could  scarcely  act  as  agents  in  spreading  fungus  species  from 
wood  to  wood  when  these  are  separated  by  considerable  distances. 
That  slugs  find  a  fruit-body  palatable  is  no  proof  that  they  are 
the  agents  for  distributing  the  species  to  which  it  belongs.  In 
this  connection  we  may  consider  the  case  of  Polyporus  squamosus. 
Its  fruit-bodies  are  much  relished  by  slugs.  I  have  known  them, 
when  young,  so  persistently  visited  and  so  voraciously  eaten  that 
they  have  been  utterly  ruined  and  have  ceased  development. 
Now  in  nature  the  trees  on  which  the  fungus  occurs  are  usually 
a  considerable  distance  apart,  rarely  less  than  several  hundred 
yards  and  frequently  much  further.  Moreover,  the  fruit-bodies, 


228  RESEARCHES   ON  FUNGI 

as  a  rule,  are  produced  at  some  height  from  the  ground.  For  a 
slug,  the  infected  trees  are  often  several  days'  journey  apart,  and, 
even  if  a  slug  were  to  travel  directly  from  one  to  another,  spores 
swallowed  on  one  tree  would  all  be  lost  in  the  faeces  before  the 
next  had  been  reached.  From  a  consideration  of  the  distribution 
of  the  fungus  and  of  the  movements  of  slugs  it  seems  impossible 
that  these  animals  should  materially  help  in  spreading  the  species 
from  tree  to  tree.  A  similar  argument  might  be  applied  to 
Pleurotus  ulmarius  and  many  other  species  growing  on  trees, 
as  well  as  to  such  fungi  as  grow  on  the  ground  and  are  characterised 
by  the  fruit-bodies  developing  sporadically  at  considerable  distances 
from  one  another.  The  Russulse,  Amanitse,  &c.,  exhibit  all  the 
usual  arrangements  in  their  fruit-bodies  for  liberating  the  spores 
into  the  air  in  such  a  manner  that  they  may  be  carried  off  by  the 
wind.  In  the  absence  of  slugs,  hundreds  of  millions  of  spores 
fall  from  the  gills.  We  can  scarcely  suppose  that  spores  thus 
carried  off  by  the  wind  have  no  chance  of  reproducing  the  species. 
It  seems  probable,  therefore,  that  the  wind,  even  in  the  case  of 
the  Russulse,  is  still  by  far  the  chief  agent  in  spreading  the  fungi 
from  place  to  place. 

The  conditions  necessary  for  the  germination  of  the  spores  of 
many  of  the  higher  fungi  in  nature  are  unknown.  Voglino's 
observations  suggest  that  small  herbivorous  animals  provide  these 
conditions  much  more  often  than  has  hitherto  been  supposed.  It 
was  recorded  in  Chapter  V.  that  a  single  Mushroom  (Psalliota 
campestris),  with  a  diameter  of  8  cm.,  produced  1,800,000,000  spores. 
We  are  justified  in  supposing  that  a  very  large  Agaric  might 
produce  4,000,000,000.  If  these  were  scattered  uniformly  in  nature 
there  would  be  sufficient  of  them  to  provide  one  for  every  square 
inch  in  a  square  mile.  This  calculation  may  perhaps  serve  to 
indicate  how  widely  dispersed  the  spores  of  one  of  the  Hymeno- 
mycetes  may  become,  and  how  frequently  they  must  be  present 
on  grass,  leaves,  fruits,  &c.  Herbivorous  birds,  toads,  slugs,  insects . 
worms,  &c.,  must  very  frequently  devour  spores  with  their  food. 
Perhaps  then,  whilst  in  general  the  wind  is  the  chief  agent  in 
dispersing  the  spores  of  Hymenomycetes,  in  some  species  small  herbi- 
vorous animals  provide  the  conditions  for  their  germination  and  the 


SLUGS   AND   HYMEXOMYCETES 


229 


production  of  a  mycelium.  It  seems  not  at  all  impossible,  for 
instance,  that  the  spores  of  a  species  of  Russula  or  Lactarius  might 
be  carried  several  miles  from  one  wood  to  another,  and  that  after 
settling  they  might  be  eaten  with  other  vegetation  by  slugs :  the 
spores  might  then  germinate  in  the  fceces  of  these  animals,  and 
the  mycelium  thus  produced  might  make  its  way  into  the 
vegetable  mould  of  the  forest  floor. 

The  fruit-bodies  of  certain  species  of  Hymenomycetes  appear 
to  be  protected  from  destruction  by  slugs  owing  to  the  presence 
in  their  cells  of  nauseous  or  distasteful  substances.  In  the 
summer  of  1904  I  began  to  investigate  the  relations  of  slugs 
to  fungi,  but  unfortunately,  owing  to  my  removal  to  Winnipeg, 
/the  work  was  interrupted,  and  I  have  not  found  opportunity  up 
to  the  present  to  resume  it.  Such  results  as  were  obtained  five 
years  ago  are  embodied  in  the  accompanying  Table.  The  obser- 
vations on  Omphalia,  Hypholoma,  and  Cantharellus  were  kindly 
made  for  me  by  Miss  J.  S.  Bayliss.  Before  each  test  the  slugs 
were  starved  for  about  two  days. 

Slugs  and  Hymenomycetes. 


Species  of  Slugrs. 

Fungus  Fruit-bodies. 

Limax 

Arion 

Auriolimax 

maxiinus. 

1      subfuscns. 

agrestis. 

Armillaria  mellea 

i             E 

E 

E 

Russula  emetica  . 

E 

E 

E 

Amanita  muscaria 

1           E 

E 

E 

Amanita  rubescens 

E 

E 

N 

Omphalia  umbellifera  . 

i           E 

— 

E 

Lactarius  rufus    . 

;           S 

— 

S 

Lactarius  glyciosmus   . 
Hygrophorus  pratensis 
Hygrophorus  virgineus 
Hypholoma  fasciculare 
Laccaria  laccata   . 

S 
i          S 

N 
N 

N 

N 
N 
N 

N 

Cantharellus  lobatus    . 

— 

— 

N 

E  =  fruit-bodies  readily  eaten ; 

S  =  fruit-bodies  slightly  eaten  and  evidently  disliked  ; 

N  =  fruit-bodies  not  eaten  at  all,  so  far  as  could  be  seen,  the  slugs  preferring 

starvation  to  feeding  ; 
—  =  no  experiment. 


230  RESEARCHES   ON   FUNGI 

The  results  just  given  indicate  that,  whilst  species  of  Armillaria, 
Russula,  Amanita,  and  Omphalia  are  relished  by  the  slugs  tested, 
species  of  Lactarius,  Hygrophorus,  Laccaria,  Hypholoma,  and 
Cantharellus  are  disliked  to  a  greater  or  less  extent. 

Lactarius  rufus  to  our  taste  is  exceedingly  acrid,  and  its 
peculiar  latex  may  well  be  the  cause  of  its  being  but  very  slightly 
eaten  by  hungry  slugs.  In  nature,  among  thousands  of  fruit- 
bodies  of  this  species,  I  have  very  rarely  found  one  slug-eaten, 
and  then  very  slightly.  Once  a  specimen  was  noticed  which, 
from  the  slime  left  all  over  the  gills,  had  evidently  been  visited 
by  a  slug,  but  which  had  not  been  attacked ;  whereas  fruit- 
bodies  of  Russula  citrina  close  by  had  been  seriously  damaged. 
This  seems  to  afford  distinct  evidence  that  the  one  species  is 
chemically  protected  from  slugs  and  that  the  other  is  not. 
Lactarius  glyciosmus  contains  a  peculiar  aromatic  substance,  and 
it  may  be  this  which  causes  the  fruit-bodies  to  be  left  uneaten 
by  Agriolimax  agrestis. 

The  fruit-bodies  of  most  species  of  Hygrophorus  are  glutinous 
or  viscid  and  their  gills  are  waxy.  Possibly  it  is  their  physical 
nature  which  renders  them  distasteful  to  slugs.  The  exact  causes 
which  render  these  and  other  fruit-bodies,  such  as  those  of 
Hypholoma  fasciculare  and  Laccaria  laccata,  inedible,  require 
further  investigation. 

Mere  acridity  of  itself  is  not  sufficient  to  cause  a  fungus  to  be 
rejected  by  slugs.  Every  one  is  agreed  that  the  fruit-bodies  of 
Russula  emetica  are  very  acrid;  yet  all  three  species  of  slugs 
tested  eat  them  with  avidity. 

Slugs  can  feed  upon  a  number  of  fruit-bodies  which  are 
poisonous  to  man.  Thus  Amanita  muscaria  was  eaten  vora- 
ciously by  all  three  of  the  slugs  tested  and  without  any  ill  effects 
to  them.  Amanita  phalloides  is  one  of  the  most  poisonous 
of  fungi,  and  yet  in  nature  one  may  often  find  slug-eaten  fruit- 
bodies  of  this  species.  It  is  evident  that  muscarine,  phalline,  and 
other  toxines  present  in  species  of  Amanita  have  no  protective 
significance  so  far  as  slugs  are  concerned. 


PART    II 

SOME   OBSERVATIONS   UPON  THE   DISCHARGE  AND   DIS- 
PERSION  OF   THE   SPORES   OF   ASCOMYCETES   AND 
OF   PILOBOLUS 


CHAPTER   I 

THE  DISPERSION  OF  SPORES  BY  THE  WIND  IN  ASCOMYCETES— 
PUFFING— THE  PHYSICS  OF  THE  ASCUS  JET  IN  PEZIZA— THE 
FIXATION  OF  THE  SPORES  IN  THE  ASCUS  OF  PEZIZA  REPANDA 
—COMPARISON  OF  THE  SIZES  OF  WIND-BORNE  SPORES  IN 
ASCOMYCETES  AND  HYMENOMYCETES— THE  HELVELLACEyE. 

NOT  only  in  the  Hymenomycetes,  but  also  in  many  other  fungi, 
beautiful  adaptations  are  to  be  found  by  which  the  spores  are 
suitably  dispersed,  but- in  most  instances  the  mechanism  involved 
still  awaits  a  careful  analysis  from  the  point  of  view  of  physics. 

In  the  majority  of  the  Ascomycetes,  the  ascus  is  an  explosive 
mechanism  of  considerable  power,  and  it  often  shoots  out  its  spores 
to  a  distance  of  one  or  several  centimetres,  thus  causing  them  to 
become  effectively  separated  from  the  sporocarp.  It  was  pointed 
out  in  the  first  chapter  of  Part  I.  that  the  profound  differences 
between  Hymenomycetes  and  Ascomycetes  in  the  position  occupied 
by  the  hymenial  surfaces,  and  in  the  structure  of  the  fruit-bodies, 
are  correlated  with  the  equally  profound  differences  between 
basidia  and  asci  as  spore-discharging  mechanisms. 

The  dispersal  of  ascospores  after  ejection  from  the  ascus  appears 
in  many  cases  to  be  brought  about  either  by  the  wind  or  by  her- 
bivorous animals.  I  regard  it  as  a  distinct  matter  of  importance 
which  of  these  two  means  of  dispersal  is  employed,  for  each  of 
them  is  associated  with  a  particular  type  of  ascus.  As  examples 
of  Ascomycetes  with  wind-dispersal  may  be  mentioned  Gyromitra 
esculenta,  Morchella  gigas,  Bulgaria  polymorpha,  and  Peziza 
aurantia,  whilst  Ascobolus  immersus  and  Saccobolus  may  be 
regarded  as  representing  those  forms  which  are  spread  by  her- 
bivorous animals.  It  is  probable  that  there  are  some  species  of 
Ascomycetes  which  have  an  intermediate  type  of  spore-dispersal, 
corresponding  to  that  associated  with  coprophilous  Hymenomycetes, 
in  which  the  spores  are  first  scattered  by  the  wind  and  subsequently 


234  RESEARCHES   ON   FUNGI 

become  redispersed  by  herbivora.  In  these  species  it  is  to  be 
expected  that  the  structure  of  the  ascus  would  be  correlated  with 
wind-dispersal. 

The  Dispersal  of  Spores  by  the  Wind  in  some  Ascomycetes. — 
According  to  Falck,1  in  Gyromitra  esculenta — one  of  the  Helvel- 
lacese  —  the  spores,  after  being  shot  out  of  the  ascus,  become 
separated  from  one  another  and  settle  singly;  and  I  have  noticed 
a  similar  phenomenon  in  Bulgaria  polymorpha  (Wettst.).  Doubt- 
less, in  both  these  species,  the  spores,  which  are  no  larger  than 
those  of  many  Hynienomycetes,  are  carried  away  from  the  fruit- 
bodies  by  the  wind. 

Plowright2  watched  the  discharge  of  the  spores  of  Morchella 
gigas  one  evening  with  the  aid  of  an  oblique  beam  of  sunlight. 
He  observed  that  the  head  of  each  Morel  was  surrounded  by  a 
cloud  of  spores  extending  3  or  4  inches  around  it.  He  states 
that  "This  cloud  could  only  be  seen  in  the  oblique  light  against 
a  dark  background.  When  acted  upon  by  a  gentle  current  of 
air,  such  as  would  be  produced  by  gently  waving  the  hand,  it 
swayed  to  and  fro  without  manifesting  any  tendency  to  become 
dispersed.  The  component  sporidia  were  in  constant  motion, 
rising  and  falling  and  circling  about,  as  if  the  law  of  gravity 
were  a  myth,  existing  only  in  the  imagination  of  philosophers. 
When  the  cloud  was  quite  blown  away  by  a  more  powerful  air- 
current,  it  in  the  course  of  a  few  seconds  reformed.  The  contents 
of  each  ascus  could  be  seen  to  be  separately  ejected  in  a  minute 
jet  consisting  of  a  limited  number  of  sporidia,  which  speedily 
became  lost  with  the  others  forming  the  cloud."  From  this 
description  it  seems  evident  that  the  cloud  of  spores  which  forms 
above  a  fruit-body  of  a  Morchella  is  very  similar  to  that  which 
forms  under  the  pileus  of  a  Hymenomycete,  such  as  a  Mushroom 
or  a  Polyporus.  In  both  clouds  the  spores  are  separated  from 
one  another  and  fall  so  slowly  through  the  air  that  they  can 
readily  be  carried  off  by  very  slight  air- currents. 

1  R.  Falck,  "  Die  Sporenverbreitung  bei  den  Basidiomyceten,"  Beitrage  zur  Biol. 
der  Pftanzen,  Bd.  IX.,  1904,  p.  51. 

2  C.  B.  Plowright,  "On  Spore  Diffusion  in  the  larger  Elvellacei,"  Grevillea, 
vol.  ix.,  1880-81,  p.  47. 


ASCOMYCETES   AND   WIND   DISPERSAL 


235 


We  shall  now  consider  the  phenomenon  of  the  separation  of 
the  spores  from  one  another,  just  after  discharge  from  the  ascus. 
That  this  actually  occurs  in  some  and  probably  in  very  many 
species  seems  to  me  to  be  conclusively  proved  by — (1)  The  definite 
observation  by  Falck x  that  the  spores  of  Gyromitra  esculenta 
settle  singly,  and  a  similar  observation  by  myself  upon  Bulgaria 
polymorpha  ;  (2)  the  just  quoted  description  by  Plowright  of 
spore-discharge  in  Morchella  gigas ; 
and  (3)  some  observations  upon  '•: 

the  discharge  of  individual  asci  of 
Peziza  which  have  been  made  by 
my  laboratory  attendant,  Mr.  C. 
W.,  Lowe,  and  myself.  Mr.  Lowe 
has  informed  me  that  h&  watched 
the  discharge  of  spores  from  a 
fruit-body  of  Peziza  aurantia  be- 
neath an  electric  lamp  with  a 
lens.  He  states  that  each  indi- 
vidual ascus  jet  appeared  to  break 
up  at  a  distance  of  from  2  to  2*5 
cm.  from  the  top  of  the  fruit-body, 
and  that  in  one  instance  on  the 
breaking  up  of  a  jet,  he  was  able 
to  count  six  separated  spores. 
With  the  help  of  my  beam-of-light  method  I  have  fortunately  been 
able  to  repeat  and  extend  these  observations. 

A  fruit-body  of  Peziza  repanda  (Fig.  77)  came  up  upon  horse 
dung  in  the  laboratory.  When  ripe,  it  was  placed  upright  in  the 
middle  of  a  covered  glass  jar,  6  inches  high  and  4  inches  in 
diameter ;  and  a  strong  beam  of  light  was  directed  through  the 
air  immediately  above  the  hymenium.2  I  then  observed  that 
the  asci  discharged  their  contents  into  the  air  successively,  at 
intervals  of  a  few  seconds.  Although  in  the  course  of  two  or 
three  hours  I  watched  the  discharge  of  several  hundred  asci,  in 
no  case  was  I  able  to  detect  an  ascus  jet  taking  its  upward  flight 


FIG.  77. — The  discharge  of  spores  from 
Peziza  repanda,  f,  section  of  a  fruit- 
body  covered  above  with  the  hymenium 
A  and  supported  by  a  stipe  with  a  root- 
ing base  ;  d,  horse  dung  ;  g,  glass  base 
of  the  culture  dish.  Above  the  hyme- 
nium are  shown  several  groups  of  eight 
spores  as  seen  in  a  concentrated  beam 
of  light  immediately  after  their  dis- 
charge from  the  asci.  Natural  size. 


1  R.  Falck,  loc.  cit. 


2  Cf.  Part  I.,  Chap.  VII. 


236  RESEARCHES   ON  FUNGI 

into  the  air.  The  discharged  contents  of  each  ascus  always  made 
their  first  appearance  as  eight  spores  which  had  already  separated 
from  one  another,  and  which  were  falling  very  slowly  downwards 
at  a  distance  above  the  hymenium  of  about  2-3  cm.  (Fig.  77). 
The  sudden  bursting  into  view  of  the  eight  glistening  and  falling 
particles  against  a  black  background  forcibly  reminded  me  of  the 
sudden  illumination  of  the  sky  at  night  by  a  shower  of  brilliant 
points  of  light  produced  by  an  explosive  rocket.  The  eight  spores 
of  each  ascus,  at  the  moment  of  their  appearance  in  the  beam  of 
light,  usually  formed  a  more  or  less  regular  vertical  series  in  which 


FIG.  78. — Semi  diagrammatic  sketch  of  a  section  through  a  fruit-body  of  Feziza  rcpanda 
whilst  discharging  its  spores.  The  spores  are  shot  up  to  a  height  of  1-2-5  cm. 
above  the  hymenium  and  are  then  carried  off  by  the  wind.  Natural  size. 


the  highest  spore  was  several  millimetres  from  the  lowest.  It  was 
observed  that  very  slight  air-currents  were  sufficient  to  carry  the 
separated  spores  round  and  round  in  the  air  contained  within  the 
glass  jar.  It  can  scarcely  be  doubted,  therefore,  that  the  spores 
of  the  Peziza  are  dispersed  in  nature  by  the  wind  in  the  same 
manner  as  those  of  Hymenomycetes.  It  is  interesting  that  the 
cloud  of  spores  produced  by  the  Peziza  comes  into  being,  not 
immediately  above  the  hymenium,  but  at  a  distance  of  2-3  cm. 
above  it.  This  enables  horizontal  air-currents  which  are  almost 
universally  found  above  the  surface  of  the  ground  to  carry  away 
the  spores  before  they  have  time  to  fall  back  on  to  the  fruit-body 
from  which  they  have  been  discharged  (Fig.  78). 


PUFFING  237 

Puffing.— The  normal  method  of  spore-discharge  from  Peziza  re- 
panda  under  natural  conditions  is  probably  a  more  or  less  successive 
discharge  of  ripe  asci,  the  spore-discharge  period  lasting  for  some  days. 
A  similar  gradual  emptying  of  the  asci  has  been  observed  in  other 
Peziza?,  in  Helvella,  Morchella,  Bulgaria,  Exoascus,  &c.x  When  a 
fruit-body  of  Peziza  repa-nda  was  left  undisturbed  for  some  hours  in 
a  damp-chamber  it  ceased  to  liberate  its  spores.  The  beam  of  light 
showed  that  none  of  the  asci  were  discharging  their  contents. 
However,  when  the  glass  plate  covering  the  culture  vessel  was 
raised  and  the  hymenium  was  rubbed  with  a  match-stick  or  other 
rod,  a  considerable  number  of  asci  burst  almost  simultaneously  and 
spore-discharge  continued  for  at  least  an  hour.  According  to  De 
Ba^ry,  the  simultaneous  discharge  of  a  large  number  of  asci — the 
phenomenon  known  as  "  puffing " — may  be  caused  in  Peziza 
acetabulum,  P.  sclerotiorum,  and  Helvella  crispa  by  shaking  a  fruit- 
body,  or  by  suddenly  allowing  a  fruit-body  which  has  previously 
been  kept  in  a  damp-chamber  to  come  into  contact  with  dry  air.2 
He  further  found  that  the  bursting  of  isolated  ripe  asci  when  lying 
in  water  can  be  brought  about  "  by  exposing  them  to  the  operation 
of  agents  like  alcohol  and  glycerine,  which  withdraw  their  water."  3 
He  came  to  the  conclusion  that  loss  of  water  causes  puffing  "  by 
altering  the  state  of  tension  in  each  ascus  either  by  lessening  the 
expansion  of  the  lateral  walls  and  so  increasing  the  pressure  of  the 
fluid  contents  on  the  place  of  dehiscence,  or  by  lessening  the  power 
of  the  place  of  dehiscence  to  resist  the  pressure  which  remains 
unaltered." 4  Massee 5  has  pointed  out  that  this  explanation  is  not 
entirely  satisfactory,  "  as  fungi  will  often  puff,  after  lying  in  a  room 
for  some  hours,  if  moved."  In  Peziza  rej)anda  I  have  found  that 
mere  rubbing  without  change  of  atmospheric  conditions  was  suffi- 
cient to  cause  some  of  the  asci  to  burst.  The  simplest  explanation 
of  these  two  observations  seems  to  be  a  mechanical  one.  One  may 
suppose  that  at  any  one  time  the  hymenium  of  a  mature  sporocarp 
contains  a  number  of  asci  which  have  almost  reached  the  critical 

1  De  Bary,  Comparative  Morphology  and  Biology  of  the  Fungi,  Mycetozoa,  and 
Bacteria,  English  translation,  1887,  p.  89. 

2  Ibid.,  p.  90.  3  Ibid.  *  Ibid. 
6  G.  Massee,  British  Fungus  Flora,  1895,  vol.  iv.  p.  4. 


238  RESEARCHES   ON  FUNGI 

bursting  stage  of  development,  and  that  the  rubbing  or  shaking 
simply  causes  the  premature  bursting  of  a  few  such  asci  owing  to 
their  equilibrium  having  been  mechanically  disturbed.  According 
to  this  theory,  the  discharge  of  the  asci  may  be  likened  to  the 
premature  bursting  of  the  capsules  of  Impatiens,  which  one  may 
bring  about  by  slight  alternate  compression  and  relaxation  with  the 
fingers.  However,  it  seems  to  me  not  unthinkable  that  the  rubbing, 
shaking,  or  moving  of  a  fruit-body  may  serve  to  stimulate  the  proto- 
plasm in  the  asci  in  some  way  so  that  it  reacts  in  such  a  manner  as 
to  cause  the  asci  to  explode. 

I  have  tried  the  effect  of  various  chemical  substances  upon  the 
discharge  of  ripe  asci  lying  in  water,  and  I  have  been  unable  to 
confirm  De  Bary's  statement  that  bursting  of  the  asci  can  be  brought 
about  by  agents  which  withdraw  water  from  them.  Sections  through 
the  ripe  hymenium  of  Peziza  repanda  were  cut  and  mounted  in 
water  on  microscope  slides  in  the  usual  manner.  In  order  to  test  its 
effect  upon  the  asci,  a  solution  of  a  salt  or  other  substance  was  then 
run  under  the  cover-glass  gradually.  It  was  found  that  strong 
solutions  of  glycerine,  sodium  chloride,  potassium  nitrate,  and  grape 
sugar  did  not  cause  explosions  to  occur.  The  sodium  chloride, 
potassium  nitrate,  and  grape  sugar  led  to  considerable  contraction 
in  the  volume  of  the  asci,  so  that  it  is  evident  that  mere  withdrawal 
of  water  from  asci  is  not  sufficient  to  cause  them  to  explode.  On 
the  other  hand,  solutions  of  iodine,  mercuric  chloride,  silver  nitrate, 
copper  sulphate,  sulphuric  acid,  acetic  acid,  and  alcohol  gave  rise  to 
very  marked  puffing.  A  very  active  discharge  of  spores  took  place 
as  soon  as  the  asci  came  well  into  contact  with  these  substances.  In 
a  number  of  instances  practically  all  the  living  asci  discharged  their 
spores,  and  a  heavy  spore-deposit  collected  a  short  distance  in  front 
of  the  ascus  mouths.  The  seven  substances  last  named  are  all 
poisonous,  whereas  the  four  which  do  not  cause  puffing  are  non- 
poisonous.  I  was  therefore  tempted  to  draw  the  conclusion  that 
poisonous  substances  cause  puffing,  whereas  non-poisonous  ones  do 
not.  However,  further  experiment  showed  that  this  rule  does  not 
hold  universally.  Strong  sodium  hydrate  poisons  the  asci  without 
causing  them  to  explode.  When  a  solution  of  this  substance  was 


PUFFING  239 

brought  into  contact  with  the  preparation,  after  a  time  the  asci  one 
by  one  contracted  suddenly  without  discharge.  Evidently  their 
turgidity  became  lost  owing  to  the  death  of  the  protoplasm  lining 
the  ascus  wall.  Sodium  carbonate  also  did  not  cause  ascus  discharge, 
although  the  asci  died  from  its  effects.  Up  to  the  present,  therefore, 
it  seems  that  non-poisonous  substances  and  alkalies  do  not  cause 
puffing,  whereas  poisonous  substances,  excluding  alkalies,  do.  Why 
alkalies  should  behave  differently  to  other  poisonous  substances 
seems  for  the  present  inexplicable. 

In  one  experiment  an  ascus  was  caused  to  contract  considerably 
with  potassium  nitrate.  It  did  not  explode.  It  was  then  restored 
to  its  former  size  by  placing  it  in  water.  When  brought  into  contact 
with  iodine  dissolved  in  water,  it  immediately  exploded  without 
undergoing  any  preliminary  measurable  decrease  in  volume.  This 
observation  will  serve  to  emphasise  the  difference  in  action  between 
a  neutral  salt  which  merely  withdraws  water  from  an  ascus,  and  a 
non-alkaline  poisonous  substance  which  affects  the  protoplasm. 

Asci  wrhich  have  contracted  in  volume  owing  to  loss  of  water  on 
treatment  with  a  strong  solution  of  a  neutral  salt,  may  be  caused  to 
explode  when  brought  into  contact  with  iodine.  The  explosions 
under  these  conditions  are  naturally  comparatively  weak,  and  the 
spores  shot  out  from  the  asci  travel  but  a  very  short  distance  from 
the  ascus  mouth. 

The  experiments  just  recorded  seem  to  me  to  suggest  that  the 
bursting  of  ripe  and  expanded  asci  is  not  brought  about  by  an 
increase  in  the  pressure  of  the  cell-sap  upon  the  ascus  lid,  but  rather 
by  an  alteration  in  the  strength  of  attachment  of  the  ascus  lid  to  the 
rest  of  the  ascus  wall.  We  may  regard  the  protoplasm  at  the  end  of 
the  ascus  as  specially  entrusted  with  the  work  of  loosening  the 
attachment  of  the  ascus  lid,  as  its  final  duty.  By  suitable  stimula- 
tion of  this  guardian  protoplasm,  the  attachment  may  be  indirectly 
loosened  and  thus  an  ascus  explosion  brought  about.  Possibly  the 
necessary  stimulus  can  be  given  mechanically,  as  when  a  sporocarp 
is  caused  to  puff  by  mere  moving  or  shaking;  possibly  it  may  be 
given  by  a  sudden  withdrawal  of  water  from  the  end  of  the  ascus,  as 
when  a  sporocarp  is  caused  to  puff  by  suddenly  allowing  it  to  come 


240  RESEARCHES   ON  FUNGI 

in  contact  with  dry  air ;  but  it  seems  certain  that  it  can  be  given  by 
chemical  means,  as  when  an  ascus  is  caused  to  explode  when  treated 
with  silver  nitrate,  mercuric  chloride,  alcohol,  and  certain  other 
poisonous  substances.  Where  there  is  a  gradual  emptying  of  ripe 
asci,  as,  according  to  De  Bary,  occurs  in  Bulgaria,  Exoascus,  &c., 
probably  the  activity  of  the  guardian  protoplasm  is  controlled  by 
stimuli  arising  from  internal  developmental  changes  taking  place  in 
the  ascus  as  a  whole. 

At  present  there  does  not  seem  to  be  any  evidence  that  puffing 
takes  place  under  natural  conditions,  and  it  would  therefore  be 
fruitless  to  discuss  whether  or  not  the  phenomenon  has  any  useful 
biological  significance.  It  may  be  added  that  puffing,  when  observed 
in  still  air  with  the  aid  of  a  beam  of  light,  is  a  beautiful  exhibition 
of  sporocarp  activity.  It  may  be  likened  to  the  grand  finale  of 
sky-rockets  in  a  pyrotechnic  display. 

The  Physics  of  the  Ascus  Jet  in  Peziza.— From  my  obser- 
vations upon  the  discharge  of  individual  asci,  it  is  clear  that 
the  spores  contained  within  an  ascus  jet  become  separated  from 
one  another  within  a  fraction  of  a  second,  between  the  time  that 
they  leave  the  ascus  mouth  and  the  time  that  they  suddenly 
appear  as  eight  separated  particles  in  the  beam  of  light.  We 
shall  now  inquire  into  the  nature  of  the  forces  which  serve 
to  detach  the  spores  from  one  another  during  their  ascent  into 
the  air. 

The  ascus  wall  contracts  during  the  ejection  of  the  ascus  jet, 
so  that  the  ascus  volume  becomes  reduced  to  about  one-half 
(Fig.  79,  E  and  F).  The  nature  of  the  contraction  affords  a 
strong  argument  for  the  belief  that  the  pressure  exerted  upon 
the  ascus  contents  is  greatest  at  the  beginning  of  the  discharge, 
and  that  it  diminishes  continuously  and  rapidly  during  the  dis- 
charge, so  that  it  finally  becomes  zero  when  the  discharge  has  been 
completed.  The  ascus  jet  on  leaving  the  ascus  mouth  may  be 
regarded  as  a  more  or  less  cylindrical  column  of  fluid  containing 
eight  spores  situated  in  a  row.  Owing  to  the  nature  of  the  ascus 
contraction,  it  seems  almost  certain  that  the  front  end  of  the 
ascus  jet  must  be  shot  outwards  with  the  greatest  velocity  and 
the  rear  end  with  the  least.  The  whole  jet  after  its  emission 


THE   PHYSICS   OF  THE   ASCUS  JET  241 

will    tend    to    become    elongated.       The    first    spore    will    have    a 


r  1 

s-\ 

i 
n\ 

5 

I 

E 

V 

U 

FIG.  79. — Peziza  rcpanda.  A,  a  young  unripe  fruit-body.  Natural  size.  B,  an  older 
expanded  fruit-body  which  was  discharging  spores.  Natural  size.  C,  a  vertical 
section  through  the  disc  of  B  showing  the  hymenium  h,  the  subhymenium  s,  and 
the  excipulum  e  with  an  external  brown  layer  6.  Magnification,  40.  D,  two 
septate  paraphyses  with  clavate  terminal  cells.  E,  a  ripe  ascus  containing  eight 
spores  which  are  loosely  attached  to  one  another  and  are  suspended  in  a  subterminal 
position  by  a  filament  probably  composed  of  protoplasm.  F,  a  contracted  ascus 
just  after  the  spores  have  been  discharged.  G,  the  end  of  an  ascus  in  which  only 
partial  spore-discharge  had  taken  place.  A  spore  was  making  its  exit  endwise 
through  the  ascus  mouth.  H,  eight  separated  spores  as  seen  near  the  mouth  of  an 
ascus  just  after  discharge  into  a  fluid  medium.  The  unilateral  gelatinous  invest- 
ments, shown  within  the  ascus  at  E,  have  now  become  very  much  swollen.  I,  a 
spore  which  after  discharge  had  fallen  back  on  to  the  hymenium  and  had  then 
germinated.  The  germ-tube  gave  rise  to  two  clavate  conidiophores  bearing  minute 
conidia.  D-I  magnification,  317. 

higher  velocity  than   the   second,  the   second  a  higher   one   than 

Q 


242  RESEARCHES   ON   FUNGI 

the  third,  and  so  on.  It  seems  to  me  very  probable  that  it  is 
the  considerable  differences  in  the  initial  velocities  given  to  the 
different  spores  upon  their  discharge  which  is  the  chief  factor  in 
separating  the  spores  from  one  another  during  their  upward  flight 
into  the  air.  There  is,  however,  another  factor  which  must  be 
concerned  with  the  breaking  up  of  the  ascus  jet,  namely,  surface 
tension. 

It  has  been  found  both  by  mathematics  and  experiment  that 
the  equilibrium  of  a  free  cylinder  of  any  liquid,  under  the  in- 
fluence of  surface  tension  only,  becomes  unstable  as  soon  as  the 
length  exceeds  TT  times  the  diameter  ;  and  it  is  regarded  as  a 
necessary  consequence  of  this  that  such  a  cylinder,  if  once  realised, 
will  spontaneously  split  into  as  many  equal  and  equidistant  spheres 
as  TT  times  the  diameter  is  contained  in  the  length.1 

Thus  if  n  be  the  number  of  drops, 

I  the  length,  and 
d  the  diameter  of  the  cylinder, 

the  law  of  segmentation  is  expressed  by  the  formula 


From  this  formula  we  can  calculate  that,  if  the  length  of  a 
cylindrical  column  of  fluid  is  twenty-five  times  the  diameter,  the 
column  will  break  up  under  the  influence  of  surface  tension  into 
eight  separate  drops.  It  seems  to  be  a  simple  inference  from  this 
that,  if  in  a  minute  cylinder  of  this  kind  there  were  placed  eight 
equidistant  solid  spheres  with  diameters  equal  to  the  diameter 
of  the  cylinder,  then  the  cylinder  would  break  up  in  such  a 
manner  that  each  spherical  body  would  become  separated  from 
its  neighbours  and  enclosed  within  a  film  of  fluid.  The  ascus 
jet  must  be  at  first  essentially  a  cylindrical  liquid  column  con- 
taining solid  oval  nuclei  at  intervals.  Probably  the  spores  are 
ejected  end-wise  through  the  contractile  ascus  mouth  so  that 
they  come  to  have  their  long  axes  in  the  same  direction  as  the 
long  axis  of  the  jet.  As  the  jet  becomes  elongated,  owing  to  its 

1  A.  M.  Worthington,  "On  the  Spontaneous  Segmentation  of  a  Liquid  An- 
nulus,"  Proc.  of  the  Roy.  Soc.,  vol.  xxx.,  1879-80,  p.  49. 


THE   PHYSICS   OF  THE   ASCUS  JET  243 

parts,  beginning  with  the  front  end,  having  been  ejected  from 
the  ascus  mouth  with  successively  diminishing  velocities,  it  will 
reach  a  stage  when  the  relationship  of  its  length  to  its  diameter 
becomes  such  that  surface  tension  must  cause  it  to  break  up 
into  eight  separate  parts.  Each  tiny  column  of  fluid,  which  at 
first  must  connect  adjacent  spores,  will  become  unstable  when 
its  length  exceeds  three  times  its  diameter,  and  upon  slight 
further  elongation  it  will  snap  into  two  in  the  middle.  Since 
the  eight  spores  ejected  from  an  ascus,  on  their  first  appearance 
in  the  beam  of  light,  usually  form  a  more  or  less  vertical  series 
in  which  the  highest  spore  is  several  millimetres  above  the  lowest, 
it  seems  to  me  probable  that  the  segmentation  of  the  ascus  jet 
takes  place  almost  immediately  after  it  has  left  the  ascus 
mouth. 

If  the  ascus  is  regarded  as  a  mechanism  for  discharging  a  jet 
in  such  a  manner  that  the  jet  elongates  and  becomes  segmented 
by  surface  tension  into  eight  separate  parts,  each  part  containing 
a  spore,  then  the  structure  of  the  ascus  becomes  more  intelligible. 
The  long  cylindrical  form  of  the  ascus  and  the  size  of  the  spores 
are  such  that  the  spores  must  lie  in  a  single  row  one  behind  the 
other.  This  arrangement  favours  the  production  of  a  long  jet  in 
which  the  spores  are  situated  in  a  row.  The  oval  shape  of  the 
spores,  and  the  fact  that  their  long  diameters  are  wider  than  the 
ascus  mouth,  must  necessitate  their  being  ejected  through  the 
ascus  mouth  end-wise  (Fig.  79,  G).  Whilst  the  first  half  of  a 
spore  is  passing  through  the  contractile  ascus  mouth,  the  velocity 
of  movement  of  the  spore  is  probably  slightly  diminished;  and 
whilst  the  last  half  is  passing,  the  velocity  is  probably  slightly 
increased.  This  would  lead  to  a  separation  of  the  spores  in  the 
jet  at  the  very  beginning  of  its  formation.  The  advantage  in  an 
ascus  containing  a  number  of  spores  instead  of  one  is  probably 
to  be  found  in  the  fact  that  less  energy  would  be  required  to 
shoot  up  several  spores  from  one  ascus  at  one  time  than  would 
be  required  to  shoot  up  the  same  number  of  spores  if  each  were 
contained  in  a  separate  ascus.  The  production  of  exactly  eight 
spores  in  each  ascus  rather  than  a  few  more  or  less  may  have 
been  determined  in  the  first  place  by  convenience  in  nuclear 


244  RESEARCHES   ON  FUNGI 

division.  The  advantages  accruing  to  a  fungus  from  the  separation 
of  the  spores  of  an  ascus  after  they  have  been  cast  up  into  the 
air  are:  (1)  The  increase  in  the  number  of  separate  infecting 
particles  which  the  fungus  can  produce,  and  (2)  the  splitting  up 
of  the  mass  of  the  ascus  jet.  The  separate  parts  of  the  ascus  jet 
must  each  fall  considerably  more  slowly  than  the  ascus  jet  would 
do  if  it  remained  undivided  and  contracted  into  a  ball,  for, 
according  to  Stokes'  Law,  the  terminal  velocity  of  fall  of  a 
microscopic  sphere  varies  directly  as  the  square  of  the  radius. 
The  smaller  the  rate  of  fall  of  a  particle,  the  further  can  it  be 
transported  by  the  wind  before  settling.  The  separation  of  the 
ascus  spores  from  one  another  is  therefore  favourable  to  their 
dispersal  by  air-currents. 

It  has  been  shown  that  the  spores  of  Hymenomycetes,  when 
falling  in  air  unsaturated  with  water  vapour,  dry  up  within  a 
few  seconds  after  leaving  the  hymenium,  and  that,  in  conse- 
quence, their  rate  of  fall  often  becomes  considerably  reduced.1  In 
some  instances  it  was  found  that  the  initial  terminal  velocity 
becomes  reduced  to  one-half  or  one-third  according  to  the  degree 
of  humidity  of  the  air.  Doubtless,  in  Ascomycetes,  the  small 
film  of  liquid  on  the  exterior  of  each  separate  spore,  and  also  the 
spore  itself,  dry  up  in  unsaturated  air  within  a  few  seconds  after 
the  spore  has  been  discharged.  Evaporation,  by  decreasing  the 
size  of  the  falling  particles,  must  indirectly  decrease  their  rate  of 
fall,  and  therefore  in  the  end  be  advantageous  for  the  dissemination 
of  the  spores  by  the  wind. 

The  Fixation  of  the  Spores  in  the  Ascus  of  Peziza  Repanda. — 
In  order  to  permit  of  the  efficient  ejection  of  the  ascospores,  it  is 
necessary  that  they  should  be  situated  at  the  distal  end  of  the 
ascus ;  for  the  ascus  is  an  apparatus  which  squirts  out  only  about 
one-half  of  its  contents — the  half  nearest  the  ascus  mouth.  Zopf 
has  shown  that  in  many  cases  the  spores  are  retained  in  the 
expanded  end  of  the  ascus  by  a  special  apparatus  of  attachment: 
the  uppermost  spore  in  some  Sordariese  is  attached  to  an  inwardly 
directed  process  produced  from  the  membrane  at  the  ascus 

1  Part  I.,  Chap.  XVI. 


FIXATION   OF  SPORES   IN  THE   ASCUS  245 

apex.1  De  Bary 2  in  this  connection  said,  "  Similar  apparatus  may 
perhaps  frequently  be  in  use  especially  in  the  Pyrenomycetes.  ...  In 
many  cases,  especially  in  the  Discomycetes,  there  is  no  such  apparatus 
present,  the  spores  being  suspended  in  the  fluid  of  the  ascus.  The 
spores  must  have  nearly  the  same  specific  gravity  as  the  fluid; 
if  not,  they  would  change  their  position  as  the  ascus  changes  its 
inclination,  which  they  do  not  do.  Most,  if  not  all,  spores  produced 
in  asci  sink  in  pure  water;  the  fluid  contents  of  the  ascus  must 
therefore  be  of  greater  specific  gravity  than  pure  water,  since  it 
holds  in  suspension  bodies  of  greater  specific  gravity  than  water. 
If  increase  in  the  amount  of  the  fluid  contents  causes  the  apical 
portion  of  the  ascus  to  stretch  more  than  the  other  parts,  currents 
must  be  set  up  in  the  fluid  in  the  direction  of  the  apex  and  continue 
as  long  as  the  expansion  continues,  and  push  the  spores  therefore 
permanently  towards  the  apex.  The  arrangements  of  the  spores 
may  then  be  affected  by  special  directions  in  the  currents  which 
we  cannot  at  present  determine,  as  well  as  by  the  conditions  of 
space  noticed  above."  This  hypothesis  of  currents  does  not  seem 
to  me  to  be  at  all  adequate  to  explain  the  position  of  the  ascospores 
at  the  end  of  the  ascus.  There  are  various  objections  of  a  physical 
character  which  may  be  made  to  it,  but  it  does  not  appear  necessary 
to  discuss  them.  On  the  other  hand,  I  shall  show  that  in  Peziza 
repanda  the  position  of  the  spores  is  attained  by  other  than  hydro- 
static means. 

In  Peziza  repanda  the  eight  spores  occupy  a  subterminal 
position,  so  that  there  is  a  short  space  between  the  first  spore  and 
the  ascus  lid  (Fig.  79,  C  and  E).  Schroter3  has  figured  an  ascus 
of  P.  repanda  with  the  first  spore  in  contact  with  the  lid.  This 
arrangement  may  often  be  seen  in  dead  asci  but  never  in  living 
ones.  Each  spore  possesses  a  firm  cell-wall,  and  in  addition  is 
coated  on  one  side  with  a  thin  oval  gelatinous  investment 
(Fig.  79,  E).  These  investments  appear  to  serve  the  purpose  of 
attaching  the  spores  to  one  another  so  that  they  cannot  slip 

1  Zopf,  Sitzsber.  d.  Berliner  naturf.  Freunde,  Feb.  17, 1880.    Cited  from  de  Bary's 
Comparative  Morphology  and  Biology  of  the  Fungi,  etc.,  English  translation,  1887,  p.  88. 

2  De  Bary,  loc.  cit. 

3  J.  Schroter,  "  Pezizinese,"  in  Die  naturlichen  Pflanzenfamilien,  by  Engler  and 
Prantl,  Teil  I.,  Abteil.  1,  p.  183,  printed  1894. 


246  RESEARCHES  ON  FUNGI 

apart.  The  group  of  eight  spores  is  attached  to  the  ascus  lid 
by  means  of  a  fine,  somewhat  granular  filament  which  has  the 
appearance  of  a  protoplasmic  bridle.  A  row  of  granules  can  be 
seen  passing  down  the  middle  of  the  gelatinous  cap  of  each  spore, 
so  that  it  seems  probable  that  the  filament  is  continued  downwards 
from  the  topmost  to  the  bottom-most  spore  (Fig.  79,  E).  It  seems 
not  unlikely  that  the  row  of  spores  is  fixed  to  the  sides  of  the 
ascus  by  other  protoplasmic  bridles,  but  I  have  not  been  able  to 
discover  them.  The  fine  terminal  filament  is  very  transparent,  and 
it  may  be  on  this  account  that  it  has  hitherto  been  overlooked. 
It  can  be  made  more  prominent  by  treatment  with  1  per  cent, 
corrosive  sublimate.  From  the  foregoing,  it  is  clear  that  in  Peziza 
repanda  the  spores  are  not  freely  floating  in  the  ascus  sap  as 
de  Bary  supposed  was  the  case  in  Discomycetes  generally,  but 
are  carefully  anchored  in  position  by  one  or  more  special  proto- 
plasmic filaments.  This  being  so,  one  can  easily  understand  how 
it  is  that  the  spores  keep  near  the  end  of  the  ascus  during  the 
stretching  period,  and  there  is  no  need  of  the  current  hypothesis 
to  explain  the  phenomenon.  Lack  of  material  has  prevented  me 
from  investigating  the  extent  to  which  protoplasmic  bridles  are 
used  for  anchoring  the  spores  in  the  asci  of  Discomycetes  generally, 
but  it  seems  probable  that  this  method  of  spore  fixation  will  be 
found  to  be  of  very  common  occurrence. 

There  can  be  no  doubt  that  in  Peziza  repanda  the  eight  spores 
in  each  ascus  are  attached  together.  They  always  appear  to  be  in 
intimate  contact  with  one  another,  but  that  they  are  really  attached 
to  one  another  may  be  shown  in  the  following  manner.  A  section 
through  the  hymenium  (Fig.  79,  C)  is  mounted  in  water.  A  strong 
solution  of  grape  sugar  or  sodium  chloride  is  then  run  under  the 
cover-glass  of  the  preparation,  with  the  result  that  the  turgor  of 
the  asci  becomes  reduced.  When  this  has  happened  a  solution 
of  iodine  is  run  under  the  cover-glass.  The  iodine  on  coming  in 
contact  with  the  asci  causes  them  to  explode,  but  since  the  pressure 
of  the  ascus  sap  has  been  reduced,  the  explosions  are  comparatively 
weak.  Sometimes  the  spores  are  not  all  shot  out  of  the  ascus 
(Fig.  79,  G),  and  in  some  cases  they  are  only  just  ejected  from  the 
ascus  mouth.  When  the  latter  has  happened,  one  sometimes  sees 


FIXATION   OF  SPORES   IN  THE   ASCUS  247 

the  ejected  spores  placed  end  to  end,  one  behind  the  other,  so  as 
to  form  a  continuous  chain.  It  is  highly  improbable  that  a  group 
of  ejected  spores  should  form  such  a  chain  if  they  were  not  really 
attached  together. 

When  a  section  through  the  hymenium  of  Peziza  repanda  is 
mounted  in  water,  the  asci  are  fully  turgid.  If  such  asci  are 
caused  to  explode  by  bringing  a  solution  of  iodine  into  contact 
with  them,  the  spores  are  discharged  to  a  distance  from  the  ascus 
mouths  about  equal  to  the  length  of  the  asci.  When  vigorously 
discharged  in  this  manner,  the  eight  spores  are  shot  out  so  quickly 
that  one  can  see  nothing  of  them  as  they  pass  through  the  fluid 
medium.  The  eight  spores  suddenly  come  into  sight  in  front  of 
the  ascus  which  has  discharged  them.  They  are  then  not  travelling 
horizontally  but  merely  sinking  in  the  fluid.  On  their  first  appear- 
ance they  are  all  separated  from  one  another  in  the  manner  represented 
in  Fig.  79,  H.  The  very  transparent,  unilateral,  gelatinous  cap  on 
each  spore  then  swells  up  considerably,  doubtless  owing  to  the 
absorption  of  water.  Running  down  the  middle  of  each  cap  is 
a  row  of  granules,  which  are  doubtless  the  same  as  those  shown 
in  Fig.  79,  E,  and  therefore  the  remains  of  the  suggested  extension 
of  the  protoplasmic  bridle  over  the  spores. 

The  attachment  of  the  eight  spores  of  an  ascus  to  one  another 
in  Peziza  repanda  is  not  a  firm  one  like  that  in  Ascobolus  imniersus 
(cf.  Figs.  81  and  82),  but  only  a  very  loose  one — just  strong  enough 
to  hold  the  spores  together  before  discharge,  and  therefore  of  use 
in  aiding  them  to  take  up  a  favourable  position  in  the  ascus, 
but  weak  enough  to  be  easily  broken  down  at  the  moment  when 
the  ascus  ejects  its  contents.  In  all  probability,  the  snapping  of 
the  spore  chain*  into  eight  parts  is  due  to  the  different  spores 
receiving  different  velocities  during  their  ejection,  and  takes  place 
as  the  ascus  jet  is  elongating  whilst  leaving  the  ascus  mouth. 

One  further  point  concerning  the  spores  of  Peziza  repanda 
may  here  be  mentioned.  When  a  fruit-body  is  confined  in  a 
small  closed  chamber,  many  of  the  spores,  after  being  cast  up 
into  the  air,  fall  back  again  on  to  the  hymenium.  Under  moist 
conditions  such  spores  often  germinate  and  produce  conidia,  as 
shown  in  Fig.  79,  I. 


248 


RESEARCHES   ON  FUNGI 


Comparison  of  the  Sizes  of  Wind-borne  Spores  in  Asco- 
mycetes  and  Hymenomycetes. — The  size  of  wind-borne  spores, 
which  is  so  important  a  factor  in  determining  their  rate  of  fall, 
is  doubtless  adapted  to  the  spread  of  the  spores  by  such  air- 
currents  as  ordinarily  occur  above  the  surface  of  the  ground. 
In  this  connection  it  is  a  distinctly  interesting  fact  that  although 
Ascomycetes  produce  and  then  liberate  their  spores  into  the  air 
in  a  very  different  manner  to  that  of  Hymenomycetes,  yet  in 
both  groups  of  fungi  the  order  of  magnitude  of  the  wind-borne 
spores  is  the  same.  Evidence  supporting  this  statement  is  given 
in  the  following  Table,  where  the  sizes  of  the  spores  of  a  few 
Ascomycetes  which  make  use  of  the  wind  for  dissemination 
are  compared  with  the  sizes  of  the  spores  of  a  few  well-known 
Hymenomycetes.  In  each  series  the  spores  are  arranged  accord- 
ing to  the  magnitude  of  their  short  diameters.  This  arrange- 
ment has  been  adopted  because  the  rate  of  fall  of  spores,  and 
therefore  the  ease  with  which  they  can  be  transported  by  air- 
currents,  is  chiefly  determined  by  the  size  of  their  short  diameters 
and  not  by  that  of  their  long  diameters,  since  spores  tend  to  fall 
with  their  long  axes  in  a  horizontal  position.1  The  unit  of  measure- 
ment is  I  fj,.  The  sizes  of  the  spores  of  the  Ascomycetes  are  those 
given  by  Massee.2  The  sizes  of  the  spores  of  the  Hymenomycetes 
were  measured  by  myself  and  are  taken  from  the  Table  in  Part  I., 
Chapter  XIV. 

Comparison  of  the  Sizes  of  Spores. 


Ascomycetes. 

Hymenoinycete 

8. 

species-        i  ihx°£ 

5SS 

Species. 

Short 
Axis. 

Long 
Axis. 

Bulgaria  polymorpha      .       5-6 

10-14 

(  Polyporus  squamosus 
Psalliota  campestris 

5-1 
5'5 

14-6 

7-2 

1 

I  Marasmius  oreades 

5-6 

9-5 

Peziza  aurantia       .         .      7-8 

15-16 

$  Coprinus  comatus 
I  Russula  emetica  . 

7-5 
7-5 

12-6 
8-8 

Gyromitra  esculenta       .       9-11 

17-25 

Amanitopsis  vaginata 

10-2 

10-2 

fruit-body  I. 

Morchella  gigas       .         .     11-14 

i 

21-24 

Amanitopsis  vaginata. 
fruit-body  III. 

11-7 

11-7 

1  Cf.  the  end  of  Chap.  XV.,  Part  I.          *  G.  Massee,  British  Fungiis  Flora,  vol.  iv. 


THE   HELVELLACE.E 


249 


The  Helvellaceae. — The  Helvellaceae  are  characterised  by  pos- 
sessing long  stipes  which  have  exactly  the  same  significance  as 
in  the  Hymenomycetes.  The  hyinenium  becomes  raised  up  above 
surrounding  leaves  and  herbage,  so  that  the  spores,  after  being 
discharged  from  the  asci,  can  readily  be  carried  off  by  air-currents. 
A  specimen  of  one  of  the  largest 
species  —  Morckella  crassipes  —  is 
illustrated  in  Fig.  80.  It  was  9 
inches  high  and  therefore  rivalled 
in  stature  some  of  the  largest  of 
the  Agaricinese. 

.  The  pileus  of  a  Morchella  is 
provided  with  anastomosing  ribs 
or  plates  which  enclose  irregular 
polygonal  pits.  The  hymenium 
covers  the  whole  of  the  exterior  of 
the  pileus,  so  that  it  is  evident  that 
the  plates  have  the  same  function 
as  the  gills  of  a  Mushroom :  they 
serve  to  increase  the  amount  of 
the  spore-bearing  surface.  How- 
ever, if  one  compares  the  pileus  of 
a  Morchella  with  that  of  a  Mush- 
room, one  notices  that  the  folding 
of  the  hymenium  is  vastly  more 
compact  in  the  latter  than  in  the 
former.  The  reason  for  this  is  to 
be  found  in  the  fundamental  differ- 
ence between  basidia  and  asci  as 
spore-liberating  mechanisms.  The 
spores  of  a  basidium  are  only  shot 
outwards  to  a  distance  of  about  (H  mm.,  whereas  those  of  an 
ascus  are  often  propelled  several  centimetres.  Hence  adjacent 
gill  surfaces  can  be  placed  very  near  together  without  interfering 
with  the  escape  of  the  spores.  On  the  other  hand,  the  plates  on 
a  Morchella  pileus  must  be  a  considerable  distance  apart  or  the  asci 
would  not  have  sufficient  room  for  discharging  their  contents. 


FIG.  80.— Fruit-body  of  Morchella  eras- 
sipes,  an  Ascomycete  which  resembles 
many  Hymenomycetes  in  having  its 
pileus  supported  on  a  long  stipe. 
Photographed  at  Winnipeg  by  C.  W. 
Lowe.  \  natural  size. 


25o  RESEARCHES   ON   FUNGI 

It  seems  that,  owing  to  their  possessing  basidia,  the  Hymeno- 
mycetes  are  better  adapted  to  produce  large  fruit-bodies  which 
liberate  their  spores  into  the  air,  than  Ascomycetes.  In  large 
fruit-bodies  the  hymenium  of  Hymenomycetes  can  be  much 
more  folded  than  that  of  Ascomycetes,  and  therefore  can  produce 
a  much  larger  number  of  spores.  It  may  be  on  this  account  that 
the  Hymenomycetes  have  become  the  dominant  fungi  upon  the 
vegetable  mould  of  fields  and  forests. 


CHAPTER   II 

THE  DISPERSAL  OF  THE  SPORES  OF  ASCOMYCETES  BY  HERBIVOR- 
OUS ANIMALS  ILLUSTRATED  BY  AN  ACCOUNT  OF  ASCOBOLUS 
IMMEItSUS—PILOBO'LUS,  EMPUSA  MUSGJE— LYCOPERDON— THE 
SOUND  PRODUCED  BY  THE  DISCHARGE  OF  SPORES,  WITH 
SPECIAL  REFERENCE  TO  PILOBOLUS. 

The  Dispersal  of  the  Spores  of  Ascomycetes  by  Herbivorous 
Animals,  illustrated  by  an  Account  of  Ascobolus  immersus. 
Pilobolus,  Empusa  muscw. — Ascomycetes  in  which  the  spores  after 
ejection  from  the  asci  are  dispersed  by  herbivorous  animals  develop 
on  faeces  and  have  a  coprophilous  mode  of  existence.  Of  these  the 
most  striking  examples  are  afforded  by  species  of  Ascobolus,  e.g. 
A.  immersus,  and  by  Saccobolus.  Their  spores  are  arranged  in  the 
ascus  more  or  less  in  two  rows,  and  are  held  firmly  together — in 
Ascobolus  by  their  gelatinous  coats  (Fig.  81),  and  in  Saccobolus  by 
a  special  investing  membrane.  The  object,  so  to  speak,  of  spore- 
discharge  in  these  fungi  is  to  eject  the  spores  from  the  ascus  to  as 
great  a  distance  as  possible,  so  that  they  may  fall  at  once  on  to  the 
surrounding  grass.  In  feeding,  herbivorous  animals  swallow  the 
grass  and  spores  together.  The  latter  pass  out  in  the  excrement 
uninjured  and  ready  to  germinate.  In  their  mode  of  spore-dispersal 
these  Ascomycetes  exactly  resemble  Pilobolus.  The  attachment  of 
the  eight  spores  to  one  another,  so  as  to  form  an  oval  mass,  prevents 
the  ascus  jet  being  broken  up  by  surface  tension  and  thus  keeps 
the  mass  of  the  projectile  constant.  This  enables  the  spores  to  be 
thrown  to  a  greater  distance  from  the  faecal  substratum  than  would 
otherwise  be  possible. 

For  the  sake  of  comparison  with  the  Hymenomycetes,  a  special 
investigation  was  made  upon  the  spore-discharge  of  Ascobolus 
immersus,  the  asci  and  spores  of  which  are  of  large  size  even  for  an 
Ascobolus.  The  fungus  made  its  appearance  on  a  horse-dung  culture 


252 


RESEARCHES   ON  FUNGI 


in  the  laboratory.  The  asci  were  found  to  be  heliotropic,1  and  they 
were  caused  to  point  directly  upwards  by  enclosing  the  culture  in  a 
dark-chamber  and  reflecting  light  downwards  upon  it  through  a 
small  top  window.  The  spores,  attached  together  in  groups  of  eight, 


FIG.  81. — Ascobolus  immcrsun.  a,  five  fruit-bodies,  shown  natural  size,  on 
a  section  of  horse  dung.  6,  fruit-body  with  five  asci  projecting  from 
the  hymenium  just  before  bursting.  Two  asci  belonging  to  the  next 
younger  series  are  to  be  seen  almost  hidden  among  the  paraphyses  in 
the  foreground,  c,  a  young  ascus  and  paraphyses.  d  and  e,  two  fully 
swollen  asci  isolated  from  the  hymenium.  /and  g,  burst  asci  which 
have  contracted  to  half  their  original  length.  In  /  the  lid  of  the 
ascus  has  opened  as  if  attached  by  a  hinge,  y  shows  the  result  of  an 
ascus  explosion  watched  under  water  with  the  microscope.  The  lid  i 
has  been  shot  away  along  with  the  ascospore  mass  h.  The  eight 
ascospores  are  attached  by  their  gelatinous  envelopes,  b-i  magnifi- 
cation, 70. 


were  then  discharged  in  a  vertical  direction,  so  that  they  struck  and 
adhered  to  the  underside  of  a  horizontal  glass  plate  placed  25  cm. 
above  the  fruit-bodies.  Further  experiment  showed  that  the  maxi- 
mum height  of  projection  was  about  35  cm.  The  culture  was  then 
set  in  a  large  glass  case  which  was  exposed  to  the  light  at  a  labora- 
1  For  the  significance  of  heliotropism  in  asci,  ride  Chap.  IV.,  pp.  74,  75. 


DISPERSION  BY  ANIMALS  253 

tory  window.  The  floor  of  the  case  was  covered  with  a  sheet  of 
white  paper.  After  falling  upon  the  latter,  the  ejected  groups  of 
spores  could  be  distinguished  with  the  naked  eye  as  tiny  dark 
specks.  The  maximum  horizontal  distance  to  which  any  of  them 
was  shot  was  found  to  be  about  30  cm.  In  violence  of  spore- 
discharge  possibly  Ascobolus  immersus  is  not  exceeded  by  any  other 
Ascomycete,  although  it  is  easily  beaten  by  Pilobolus,  which  can 
squirt  its  sporangia  to  a  distance  of  more  than  a  metre.  These 
performances  seem  truly  titanic  when  compared  with  those  of  the 
Hymenomycetes,  for  the  maximum  horizontal  distance  of  discharge 
of  basidiospores  was  observed  to  be  only  O01-0'02  cm.1 

A  group  of  eight  Ascobolus  spores  clinging  together  was  estimated 
to  have  a  volume  about  2000  times  greater  than  that  of  a  single  spore 
of  Amanitopsis  vaginata.  It  is  the  large  mass  of  the  united  asco- 
spores  which  permits  of  the  projectile  receiving  sufficient  initial 
velocity  to  carry  it  a  distance  of  many  centimetres.  In  order  to- 
shoot  out  a  tiny  Amanitopsis  spore  to  an  equal  distance,  a  relatively 
enormous  initial  velocity  would  require  to  be  given  to  it.  A  parallel 
case  may  be  cited  from  everyday  life.  A  good  thrower  can  throw  a 
cricket  ball  one  hundred  yards.  With  his  strongest  effort,  however,, 
he  can  throw  a  small  shot  only  a  few  feet.  If  he  were  determined 
to  make  the  shot  travel  as  far  as  the  cricket  ball  he  could  succeed  in 
doing  so  by  putting  it  into  a  gun  and  driving  it  out  with  gunpowder. 
The  very  high  initial  velocity  which  it  would  then  receive  would  be 
vastly  greater  than  that  imparted  to  the  cricket  ball,  although  the 
distance  traversed  by  both  objects  would  be  the  same.  It  is  just  as 
impossible  for  a  man  to  throw  a  small  shot  a  hundred  yards  as  it 
would  be  for  a  Mushroom  to  shoot  out  a  basidiospore  to  a  distance 
of  a  single  centimetre.  In  order  to  accomplish  the  latter  feat,  it 
would  be  necessary  for  the  spore  to  be  projected  with  an  initial 
velocity  of  the  order  of  65  metres  per  second  !2  On  the  other  hand, 
the  united  eight  spores  from  an  ascus  of  the  Ascobolus  could  be  shot 
a  centimetre  with  an  initial  velocity  of  only  0'2-0'3  metres  per  second. 

1  Chap.  XI.,  Method  II. 

2  Calculated  by  using  the  first  equation  in  Chapter  XVII.  and  taking  the 
terminal  velocity  of  a  Mushroom  spore  as  0'15  cm.  per  second  (vide  Chapter  XVI.). 
The  spore  was  assumed  to  be  spherical. 


254 


RESEARCHES   ON  FUNGI 


The  initial  velocity  which  an  ascospore  group  would  need  to  have 
imparted  to  it  in  order  to  fall  30  cm.  from  a  fruit-body  would  be  less 
than  10  metres  per  second.1 

From  the  above  discussion  it  seems  that  a  chief  factor  in  securing 
a  sufficiently  large  trajectory  for  the  ascus  contents  of  Ascobolus 

immersus  is  the  large  mass  of  the 
projectile.  The  projectile  owes  its 
L  size  to  four  factors  :  (1)  The  unusually 
large  size  of  the  spores,  (2)  the 
thick  gelatinous  envelope  round 
each  spore,  (3)  the  clinging  of  the 
c  spores  together,  and  (4)  the  large 
mass  of  the  discharged  ascus  sap. 
The  spores,  excluding  their  gela- 
j  tinous  investments,  measure  35-45 
x  55-65/A,  and  therefore  are  50-100 
times  greater  in  volume  than  the 
wind  -borne  spores  of  Peziza  aur- 
antia.  The  gigantic  size  of  the 
spores  as  compared  with  those  of 
the  Hymenomycetes  will  at  once  be 
realised  by  a  glance  at  Fig.  82. 

In  Pilobolus,  where  the  unopened 


FIG.  82.— Comparative  sizes  of  fungus 
projectiles.  «,  spore  mass  of  Ascobolus 


***    sporangium  is  squirted  off  the  spor 

pestris ;  c,  spores  of  Coprinus  comatus. 


d,  spores  of  Psalliota  com-    an<riophore,   the  projectile    is  rela- 


All  drawn  to  the  scale  given.  tively  of  great  size.     That  it  should 

be  shot  out  farther  than  the  contents  of  any  ascus  is,  for  the 
mechanical  reasons  already  discussed,  not  in  the  least  surprising. 
Empusa  muscte,  as  is  well  known,  can  send  its  unicellular  conidia 
to  a  distance  of  some  centimetres.  Here,  however,  the  spores 
are  not  only  very  large  but  become  coated  with  a  thick  and  sticky 
fluid  discharged  from  the  conidiophore.  The  large  size  of  the 
projectile  may  be  at  once  recognised  from  the  accompanying  photo- 
graph (Fig.  83). 

1  Here  the  terminal  velocity  was  taken  to  be  30-50  cm.  per  second  (vide  infra). 
The  spore-group  was  assumed  to  be  spherical.  The  calculations  are  only  very 
rough  approximations  to  actual  values. 


THE  FALL  OF  ASCOSPORES  255 

The  large  mass  of  a  group  of  eight  ascospores,  of  the  sporangium 
of  Pilobolus,  or  of  the  conidiuin  of  Empusa  musae,  is  unfavourable 
to  the  dispersion  of  these  structures  by  the  wind  owing  to  the  fact 
that  it  causes  them  to  fall  with  comparative  rapidity.  Let  us 
compare  the  terminal  vertical  velocity  of  an  Ascobolus  immersus 
ascospore  group  with  that  of  a  basidiospore  of  Amanitopsis 


FIG.  83.  —  Empusa  rnuscse.  The  house-fly  has  been  killed  by  the  fungus  and 
is  now  fixed  by  its  proboscis  to  a  window-pane.  The  halo  around  the  fly's 
body  consists  of  discharged  conidia,  many  of  which  have  been  shot  to  a 
distance  of  2  cm.  and  some  to  about  3  cm.  Photographed  by  C.  W.  Lowe. 
|  natural  size. 

vaginata.      Assuming    Stokes'   Law   and   equal   densities    for  the 
falling  particles,  it  may  be  shown  that 


where         V  =the  terminal  vertical  velocity  of  the  basidiospore, 

Vj  =  the  terminal  vertical  velocity  of  the  ascospore  group, 
a   =  the  radius  of  the  basidiospore, 

aj  =the  radius  of  a  sphere  with  a  volume  equal  to  that  of  the  ascospore 
group. 

Since,  from   measurements  made,  we   may   take   V  =  0'5   cm.   per 
second,  a  =  0'0005  cm.,  and  ^  =  0-005  cm.,  we  may  calculate  that 


256  RESEARCHES   ON   FUNGI 

Vj  =  50  cm.  per  second.  Since  V  is  only  0*5  cm.  per  second,  the 
conclusion  may  be  drawn  that  the  ascospore  group  falls  about  one 
hundred  times  more  rapidly  than  the  basidiospore.  Since  for 
high  velocities  Stokes'  Law  breaks  down  and  the  resistance  of 
the  air  becomes  proportional  to  a  higher  power  of  the  velocity, 
the  rate  of  fall  of  the  ascospore  group  is  in  reality  somewhat 
less  than  50  cm.  per  second.  Its  actual  value,  however,  must 
still  be  enormous  compared  with  that  for  the  velocity  of  fall  of  a 
basidiospore.  The  latter  was  observed  to  be  only  about  0-5  cm. 
per  second. 

Since  the  terminal  vertical  velocity  of  an  ascospore  group  of  the 
Ascobolus  has  been  calculated  to  be  of  the  order  of  50  cm.  per 
second,  we  can  easily  understand  why  it  is  that  a  thick  spore-deposit 
often  collects  within  a  short  radius  of  the  fruit-bodies.  Ordinary 
convection  currents,  such  as  occur  in  dwelling-rooms,  or  slight 
movements  of  the  air  in  the  open,  can  be  of  little  use  in  scattering 
the  ejected  ascus  contents,  although  dispersion  may  be  effected  by 
winds  of  moderate  strength.  On  the  other  hand,  basidiospores, 
owing  to  their  tiny  size,  fall  very  much  more  slowly  than  the 
ascospore  groups,  and  in  consequence  are  splendidly  adapted  for 
transport  through  the  air.  Even  very  slight  convection  currents, 
such  as  occur  almost  universally  near  the  earth's  surface,  are  able 
to  carry  them  about  and  render  the  position  where  they  come  to 
settle  a  matter  of  the  greatest  uncertainty. 

The  fruit-bodies  of  Ascobolus  immersvus  exhibit  a  number  of 
special  adaptations  to  a  coprophilous  mode  of  existence  which 
enable  them  to  liberate  their  spores  from  the  sides  of  horse-dung 
balls,  &c.,  with  success.  These  adaptations  may  be  summarised  as 
follows :  (1)  The  protrusion  of  the  ripe  asci,  just  before  discharge, 
to  some  distance  beyond  the  surface  of  the  hymenium;  (2)  the 
diurnal  periodicity  in  the  ripening  and  discharge  of  successive  series 
of  asci ;  (3)  the  heliotropic  reaction  of  the  asci  whilst  becoming 
protuberant;  and  (4)  the  great  violence  of  spore-discharge.  The 
protrusion  of  the  ripe  asci  far  beyond  the  hymenial  surface  permits 
of  the  asci  making  positive  heliotropic  curvatures.  Such  reactions 
to  light  would  be  impossible  if  the  asci  were  entirely  embedded 
in  the  hymenium  like  those  of  Pezizae.  The  periodicity  in  the 


ADAPTATIONS  IN  ASCOBOLUS  257 

ripening  of  the  asci  is  of  such  a  kind  that  each  morning  a  few 
asci  go  through  their  final  phases  of  stretching  and  discharge  their 
spores  almost  simultaneously  about  midday  or  in  the  early  after- 
noon. After  one  series  of  asci  has  exploded,  another  immediately 
begins  to  develop  which  will  discharge  its  spores  on  the  following 
day.  Owing  to  this  periodic  development  of  successive  series  of 
asci,  the  asci  always  come  to  maturity  in  daylight,  i.e.  they  always 
go  through  their  final  stretching  at  a  time  when  their  direction 
of  growth  can  be  controlled  by  heliotropic  stimuli.  The  positive 
heliotropism  of  the  asci  causes  these  structures — the  fungus  guns — 
to  become  directed  toward  well-lighted  positions  and  therefore  in 
general  toward  open  spaces.  When  the  spore-masses  are  shot 
outwards,  they  thus  come  to  have  a  good  chance  of  avoiding 
obstacles  in  their  flight  through  the  air.  The  orientation  of  the 
asci  must  prevent  a  very  large  number  of  spores  from  being  wasted 
by  being  «hot  against  adjacent  dung  balls,  &c.  We  thus  see  that 
the  protrusion  of  the  ripe  asci,  their  periodic  development,  and 
their  heliotropism  are  intimately  correlated  with  one  another.  The 
great  violence  of  spore-discharge  is  associated  with  the  unusually 
large  size  of  the  asci  and  of  the  spores.  The  clinging  of  the  spores 
together  during  discharge  and  the  large  mass  of  the  projectile,  as 
we  have  already  seen,  are  significant  in  that  they  enable  the  spores 
to  be  shot  to  a  greater  distance  from  the  horse-dung  balls  than 
would  otherwise  be  possible.  The  ascospores  are  thrown  to  such 
a  distance  that  they  fall  on  the  surrounding  herbage,  where  they 
can  be  devoured  by  herbivorous  animals  and  thus  find  their  way 
into  faeces. 

Lycoperdon. — In  Gastromycetes  the  modes  of  spore-dispersion 
are  of  various  kinds.  Sphxrobolus  steilatus  has  a  wonderful 
catapult  mechanism  for  casting  a  sac  containing  spores  a  dis- 
tance of  several  inches.  In  the  Phalloidei,1  the  fruit-bodies 
are  specialised  for  attracting  flies  by  means  of  form,  colour, 
scent,  and  sweet  juices.  In  the  Tuberaceaa,  the  hypogean 
Truffles,  &c.,  are  eagerly  sought  for  by  certain  quadrupeds  and 
other  animals.  The  main  facts  in  these  instances  are  now 
well  known  and  recognised.  However,  a  few  remarks  may  be 

1  T.  W.  Fulton,  loc.  dt. 

R 


258  RESEARCHES   ON  FUNGI 

added  on  Puff-balls.  In  the  genus  Lycoperdon,1  the  fruit-bodies 
develop  an  enormous  number  of  spores,  and  at  maturity  con- 
stitute sacs  full  of  a  dry  powder  mixed  with  capillitium 
threads.  The  peridium  breaks  away  above  so  that  each  Puff- 
ball  conies  to  have  a  more  or  less  circular  opening  at  the 
top.  The  arrangement  is  such  that  the  spores  leave  a  fruit-body 
only  when  the  wind  is  blowing  at  a  favourable  speed  for  their 
dispersion.  When  the  air  is  quiet,  the  spores  lie  safe  and  motion- 
less within  the  protecting  peridium.  As  soon,  however,  as  the 
wind  becomes  violent,  it  sweeps  in  gusts  into  the  Puff-ball  from 
above,  gradually  disengages  the  spores  from  the  capillitium 
threads,  and  bears  them  forth  to  long  distances.  A  more 
effective  mode  of  spore -dispersion  can  scarcely  be  imagined. 
In  connection  with  Puff-ball  spores  an  interesting  physical  prob- 
lem awaits  solution.  We  are  still  ignorant  why  it  is  that  the 
spores  of  Hymenomycetes  never  form  a  mass  of  loose  dust, 
whereas  this  regularly  occurs  with  those  of  a  Lycoperdon.  The 
adhesiveness  or  non-adhesiveness  of  spore  cell-walls  must  be 
recognised  as  a  matter  of  importance  in  connection  with  spore- 
dispersion. 

The  Sound  produced  by  the  Discharge  of  Spores,  with 
Special  Reference  to  Pilobolus. — Although  many  Agarics  which 
have  come  under  my  notice  shed  spores  at  the  rate  of  about 
a  million  a  minute,  I  have  never  been  able  to  detect  the  least 
sound  caused  by  spore-discharge.  So  far  as  unaided  human  ears 
are  concerned,  it  seems  likely  that  spore-emission  by  Hymenomy- 
cetes must  for  ever  be  a  quite  silent  process.  On  the  other  hand, 
the  discharge  of  spores  by  certain  Ascomycetes  appears  to  be 
distinctly  audible.  Thus  de  Bary  was  able  to  hear  "a  very  per- 
ceptible hissing  sound  produced  by  strong  specimens  of  Peziza 
acetabulum  and  Helvetia  cr-ispa." 2 

Pilobolus,  as  is  well  known,  exceeds  all  Ascomycetes  in  the 
violence  with  which  it  ejects  its  projectiles.  Coemans  records 
that  the  sporangia  can  be  projected  to  a  height  of  over 

1  Vide  Chap.  V.  p.  86. 

2  De  Bary,  Comparative  Morphology  and  Physiology  of  the  Fungi,  etc.,  English 
translation,  1887,  p.  92. 


SOUNDS  PRODUCED   BY  PILOBOLUS  259 

3  feet,1  and  Grove  found  that  on  one  occasion  the  maximum  hori- 
zontal distance  of  discharge  was  4  feet  10  inches.2  The  largest  of  all 
the  Piloboli  is  P.  loiigipes,  the  stipe  of  which  is  usually  2-3  cm. 
long,  whilst  the  diameters  of  the  sporangium  and  subsporangial 
swelling  are  0-5  mm.  and  1  mm.  respectively.  When  I  placed 
the  sporangiophores  of  this  species  so  that  they  inclined  obliquely 
upwards  at  an  angle  of  about  45°,  several  sporangia  were  shot 
more  than  5  feet  in  a  horizontal  direction,  and  one  to  a  distance 
of  6  feet  2  inches.  Grove  noticed  that,  when  a  sporangium  strikes 
one  in  the  face,  one  can  distinctly  feel  the  blow,  like  that  of  a 
small  drop  of  rain,3  and  he  called  attention  to  the  fact  that  each 
discharge  is  accompanied  "  by  a  faint  but  distinctly  audible  '  puff,' 
like  the  sound  of  a  minute  pop-gun."4  From  personal  experience 
with  a  number  of  Pilobolus  cultures,  I  am  able  to  confirm  Grove's 
statements  both  as  to  feeling  the  blows  of  the  sporangia  and  also 
as  to  hearing  the  sound  of  the  explosions.  Some  horse-dung 
cultures  of  Pilobolus  Kleinii  were  carefully  watched  during  the 
mid-day  hours  on  several  successive  days.  At  first  I  mistook  very 
slight  sounds  produced  involuntarily  from  my  collar  and  mouth  for 
sounds  proceeding  from  the  fungus.  However,  when  these  sources 
of  error  had  been  eliminated,  I  found  that  it  was  still  possible  to 
detect  some,  although  perhaps  not  all,  of  the  discharges.  On 
listening  very  intently  in  a  quiet  room,  two  sounds  were  to  be 
heard :  firstly,  a  little  click  as  a  sporangium  left  its  sporangio- 
phore,  and  secondly,  a  more  metallic  sound,  whenever  a  sporangium 
struck  the  glass  side  of  the  crystallising  dish  which  contained 
the  culture.  So  far  as  I  am  aware,  the  sound  of  the  projectiles, 
made  on  striking  obstacles,  has  not  hitherto  been  noticed.  Its 
audibility  can  be  very  much  increased  by  a  method  devised  by 
Mr.  F.  Wakefield,  who  was  assisting  me  in  the  laboratory.  One 
makes  use  of  a  drum  consisting  of  a  glass  funnel,  3  or  4  inches 
in  diameter,  across  the  mouth  of  which  a  sheet  of  thin  tissue 

1  Coemans,  Monographic  du  Genre  Pilobolus,  1860,  p.  39 ;  quoted  from  Grove's 
monograph,  p.  15. 

2  W.  B.  prove,  Monograph  of  the  Pilobolidse,  Birmingham  ;  reprinted  from  the 
Midland  Naturalist,  1884,  vol.  vii.  p.  219. 

3  Loc.  cit.,  p.  16.  4  Loc.  tit.,  p.  15. 


26o  RESEARCHES   ON  FUNGI 

paper  has  been  pasted.  If  one  holds  such  a  drum  a  little  way 
above  the  Pilobolus  culture,  one  can  readily  hear  the  bang  each 
time  a  sporangium  hits  the  tissue  paper.  I  found  that  Mr. 
Wakefield  could  detect  the  sound  made  on  the  drum  at  a  distance 
of  21  feet. 


GENERAL    SUMMARY 


The  following  is  a  summary  of  the  more  important  results  obtained 
during  the  investigations 

PART  I 

CHAPTER  I. — The  spores  of  the  Hymenomycetes  are  very  adhesive  when 
freshly  liberated.  In  consequence  of  this,  special  arrangements  are  neces- 
sary for  their  liberation  from  the  surfaces  of  gills  and  hymenial  tubes,  &c. 
Successful  liberation  can  take  place  only  when  the  hymenium  is  so  situated 
that  it  occupies  a  vertical  position  or  looks  downwards  at  a  greater  or  less 
angle. 

Paraphyses  are  useful  as  spacial  agents.  They  prevent  the  adhesive 
spores  of  adjacent  basidia  from  coming  into  contact  during  development 
and  discharge.  The  functions  of  cystidia  are  for  the  most  part  still  quite 
unknown. 

Occasionally  certain  species  of  Coprinus  give  rise  to  fruit-bodies  which 
are  normal  in  size  and  form,  but  are  either  partially  or  completely  sterile. 
The  basidia  fail  to  produce  spores.  Fruit-body  sterility  of  this  kind  was 
observed  in  Coprinus  fimetarius,  var.  cinereus,  and  also  in  an  ephemeral, 
coprophilous  species,  which  has  been  called  C.  plicatiloides. 

Fruit-bodies  are  frequently  visited  by  Springtails  (Collembola),  Mites 
(Arachnida),  and  Fungus  Gnats  (Mycetophilidse).  Their  relations  with 
these  animals  stand  in  need  of  a  detailed  investigation. 

Direct  sunlight  injuriously  affects  the  vitality  of  the  dry  spores  of 
Schizophyllum  commune  and  of  Dsedalea  unicolor.  Possibly  the  colouring 
matters  deposited  in  the  walls  of  the  spores  of  Coprini  and  of  other 
Hymenomycetes  may  serve  a  useful  purpose  by  screening  off  certain  of 
the  sun's  rays  from  the  living  protoplasm. 

CHAPTER  II. — The  disposal  of  the  hymenium  beneath  a  fruit-body  on 
gills,  on  spines,  or  in  tubes,  &c.,  instead  of  on  a  flat  surface,  is  an  economi- 
cal arrangement  which  permits  of  a  great  increase  in  the  number  of  spores 
which  a  fruit-body  of  a  given  size  may  produce.  Species  of  the  genus 
Fomes  appear  to  be  the  most  highly  specialised  in  this  respect.  The 
specific  increase  in  the  extent  of  the  hymenium  due  to  the  presence  of 
gills  and  tubes  was  measured  in  a  few  cases.  In  the  Mushroom  it  was 


262  RESEARCHES   ON  FUNGI 

found  to  be  20;  in  Fomes  vegetus  148  for  one  year,  and  500  for  three; 
whilst  in  a  large  and  old  specimen  of  Fomes  igniariun  it  proved  to  be 
nearly  1000. 

The  crowding  of  the  gills  and  the  reduction  in  diameter  of  the  tubes  in 
certain  fruit-bodies  (e.y.  those  of  the  Mushroom  and  of  Fomes  igniariuft), 
after  allowing  for  a  small  margin  of  safety,  appear  to  have  reached  their 
limits  consistent  with  the  violent  horizontal  discharge  of  the  spores  from 
the  basidia. 

CHAPTER  III. — The  fruit-bodies  of  most  species  of  Hymenomycetes  are 
very  rigid.  This  rigidity  is  of  considerable  importance  in  keeping  the 
axes  of  the  tubes  of  Polyporese,  the  planes  of  the  gills  of  Agaricinese,  &c., 
in  vertical  positions.  Slight  swaying  movements  cause  loss  of  spores.  In 
a  Mushroom  it  was  calculated  that,  when  two  adjacent  gills  are  tilted  from 
their  vertical  planes  to  an  angle  greater  than  the  critical  angle  of  about 
2°  30',  some  of  the  spores  are  unable  to  escape  from  the  interlamellar 
spaces.  With  a  tilt  of  about  5°,  half  the  spores  are  lost ;  and  with  a  tilt 
of  about  9°  30',  four-fifths  of  them.  The  rigidity  of  stipes  in  many  species 
is  secured  by  hollow  cylindrical  form  and  by  unequal  tensions  in  the  layers 
of  cells. 

CHAPTER  IV. — The  growth  movements  of  a  fruit-body  can  be  regarded 
as  so  many  adjustments  of  a  delicate  machine  made  with  the  object  of 
placing  the  hymenium  in  the  best  possible  position  for  liberating  the  spores. 
A  Mushroom  and  the  ephemeral,  coprophilous  Coprini  exhibit  four  such 
adjustments,  and  Polyporus  squamosus  five.  The  nature  of  the  adjustments 
is  correlated  with  the  general  structure  of  the  fruit- bodies  and  with  the 
orientation  of  the  substratum. 

The  amount  of  eccentricity  of  the  pileus  of  Polypoi-us  sguamosus  is  con- 
trolled by  a  morphogenic  stimulus  of  gravity. 

The  stipes  of  certain  ephemeral  Coprini,  just  before  the  pilei  expand, 
are  extremely  sensitive  to  the  stimulus  of  gravity.  When  a  stipe  had  been 
changed  from  the  vertical  to  the  horizontal  position,  a  distinct  upward 
curvature  was  noticed  after  a  stimulation  of  T5  minutes.  Another  stipe, 
similarly  displaced,  gave  a  distinct  macroscopic  reaction  to  the  stimulus  of 
gravity  after  3  minutes'  stimulation,  and  turned  through  a  complete  right 
angle,  so  as  to  regain  a  vertical  position,  in  17*5  minutes.  The  last  80° 
were  turned  through  with  a  greater  angular  velocity  than  that  of  the 
minute-hand  of  a  clock.  This  angular  velocity  is  far  greater  than  that 
known  for  any  Phanerogam,  or  indeed  any  other  plant  organ  when  stimu- 
lated by  gravity. 

CHAPTER  V. — In  perfectly  still  air,  the  spores  liberated  from  a  pileus 
placed  above  a  horizontal  sheet  of  paper  fall  vertically  downwards  and 


GENERAL  SUMMARY  263 

produce  a  spore  print  consisting  of  radiating  lines  corresponding  to  the 
inter-lamellar  spaces.  Extremely  minute  convection  currents  give  a  hori- 
zontal drift  to  the  falling  spores  and  cause  the  spore-deposit  to  become 
cloudy. 

The  number  of  spores  liberated  by  large  fruit-bodies  amounts  to  thou- 
sands of  millions.  A  specimen  of  Psalliota  campestris  with  a  diameter  of 
8  cm.  was  found  to  produce  1,800,000,000  spores,  one  of  Coprinus  comatus 
5,000,000,000,  and  one  of  Polyporus  squamosus  11,000,000,000.  The  rate 
of  elimination  of  the  spores  or  young  plants  by  death  can  be  shown  to  be 
enormous.  The  most  prolific  kind  of  fish  is  not  so  prolific  as  a  Mushroom 
plant.  It  was  estimated  that  a  large  fruit-body  (40  x  28  x  20  cm.)  of  Lyco- 
perdon  bovista,  Linn.,  the  Giant  Puff-ball,  contained  7,000,000,000,000 
spores,  or  as  many  as  would  be  liberated  by  4000  Mushrooms,  each  having 
a  diameter  of  8  cm. 

CHAPTER  VI. — With  the  unaided  eyes  by  daylight,  clouds  of  spores 
were  observed  to  be  given  off  continuously  for  thirteen  days  from  the 
underside  of  a  large  fruit-body  of  Polyporus  squamosus.  It  was  found  that 
each  hymenial  tube  was  liberating  spores  from  every  part  of  its  hymenium. 
The  visible  discharge  of  spores  appeared  to  be  unaffected  by  light  conditions 
or  by  changes  in  the  hygroscopic  state  of  the  atmosphere.  The  formation 
of  irregular  clouds,  wreaths,  and  curls  of  spores  is  not  due  to  intermittent 
spore- emission,  but  is  brought  about  by  air-currents  sweeping  beneath  the 
fruit-body. 

CHAPTER  VII. — Spores  falling  from  any  fruit-body  suspended  in  a  suit- 
able glass  chamber,  e.g.  a  closed  beaker,  can  be  seen  in  clouds  or  individually 
without  magnification  by  using  a  concentrated  beam  of  light.  Much  use 
was  made  of  this  discovery  in  the  research. 

The  beam-of-light  method  can  be  used  to  make  a  very  simple  and 
effective  laboratory  demonstration  of  the  discharge  of  spores  from  Mush- 
rooms, itc.  It  may  be  carried  out  with  great  convenience  at  any  time  by 
using  as  material  the  mature  xerophytic  fruit-bodies  of  Lenzites  betulina, 
Schizophyllum  commune,  Polystidus  versicolor,  &c.  These  can  be  kept  dry 
in  bottles  for  months  or  years.  After  wet  cotton-wool  has  been  placed 
above  them  they  quickly  revive,  and  they  begin  to  shed  their  spores  within 
six  hours.  The  emission  of  the  spores  continues  for  days. 

CHAPTER  VIII. — Spore-discharge  from  any  fruit-body  under  normal 
conditions  is  continuous.  The  period  of  spore-discharge  in  some  species 
lasts  for  a  few  hours,  in  others  days,  and  in  yet  others  for  weeks.  With 
the  beam-of-light  method  a  fruit-body  of  Schizophyllum  commune  and  also 
one  of  Polystictus  versicolor  were  both  observed  to  shed  a  continuous  stream 
of  spores  for  sixteen  days.  A  specimen  of  Lenzites  betulina  shed  spores  for 


264  RESEARCHES   ON   FUNGI 

ten  days.     These  fruit-bodies,  doubtless,  had  already  shed  spores  for  some 
time  before  they  were  gathered. 

After  the  number  of  spores  produced  had  been  estimated  and  the  length 
of  the  spore-fall  period  had  been  observed,  it  was  calculated  that  large 
fruit-bodies  of  Psalliota  campestris,  Coprinus  comatus,  Polyporus  squamosus, 
<fcc.,  shed  about  a  million  spores  a  minute  for  two  or  more  days. 

CHAPTER  IX. — The  fruit-bodies  of  corky  or  leathery  consistency  growing 
on  sticks  and  logs  are  xerophytic.  They  can  be  dried  up  without  any  loss 
of  vitality.  On  access  to  moisture  they  revive  in  a  few  hours  and  resume 
the  function  of  discharging  spores.  The  retention  of  vitality  after  desicca- 
tion in  some  species  is  continued  for  years.  The  spores  liberated  from 
revived  fruit-bodies  are  capable  of  germination.  Typical  genera  consti- 
tuting a  xerophytic  hymenomycetous  log-flora  are  :  Lenzites,  Polystictus, 
Stereum,  &c. 

The  fruit-bodies  of  Schizophyllum  commune  possess  special  adaptations 
for  a  xerophytic  mode  of  existence.  The  gills  are  partially  or  completely 
divided  down  their  median  planes  into  two  vertical  plates.  Whilst  desicca- 
tion is  proceeding,  the  two  plates  of  each  of  the  longer  and  deeper  gills 
bend  apart  and  spread  themselves  over  the  shorter  and  shallower  gills. 
When  desiccation  is  complete,  the  whole  of  the  hymenium  is  hidden  from 
external  view  and  the  fruit-body  is  covered  both  above  and  below  with  a 
layer  of  hairs.  The  closing  up  of  the  fruit-bodies  at  the  beginning  of  a 
period  of  drought  serves  to  protect  the  hymenium  from  external  enemies. 
A  fruit-body  can  retain  its  vitality  in  the  dried  and  closed-up  condition  for 
two  or  more  years.  When  allowed  to  absorb  free  water  through  the  top 
of  the  pileus,  it  revives  in  a  few  hours.  The  two  plates  of  each  pair  return 
to  their  original  vertical  positions,  and  again  become  closely  apposed.  The 
liberation  of  spores  is  then  recommenced,  and  may  last  for  some  days. 

CHAPTER  X. — The  fruit-body  in  some  species  can  only  be  developed  so 
as  to  produce  a  pileus  when  subjected  to  the  morphogenic  stimulus  of  light. 
When  a  hymenium  has  once  been  produced  it  sheds  its  spores  indepen- 
dently of  light  conditions  and  of  the  direction  of  gravitational  attraction. 

So  long  as  a  fruit-body  itself  contains  sufficient  water,  spore-discharge 
appears  to  continue  without  being  affected  by  the  hygroscopic  state  of  the 
atmosphere. 

Some  of  the  xerophytic  fruit-bodies  growing  on  logs,  &c.,  continue  to 
shed  their  spores  at  the  freezing-point  of  water.  The  range  of  temperature 
permitting  spore-discharge  in  the  case  of  Lenzites  betulina  was  found  to  be 
approximately  0°-30°  C. 

When  a  fruit-body  is  placed  in  hydrogen  or  carbon  dioxide,  the  libera- 
tion of  spores  quickly  ceases.  The  presence  of  oxygen  in  the  surrounding 
atmosphere  appears  to  be  essential  for  the  continuance  of  spore-discharge. 


GENERAL  SUMMARY  265 

In  pure  oxygen  fruit-bodies  shed  their  spores  for  several  hours  at  the  same 
rate  as  in  air. 

When  a  fruit-body  is  subjected  to  the  vapour  of  ether  or  chloroform, 
spore-discharge  ceases  almost  instantaneously,  but  can  be  resumed  when 
the  anaesthetic  has  been  removed.  A  fruit-body  of  Lenzites  betulina  re- 
covered its  spore-liberating  function  after  this  had  been  inhibited  by  ether 
vapour  for  a  week. 

CHAPTER  XI.  —  The  four  spores  on  each  basidium  are  discharged  suc- 
cessively. They  leave  the  sterigmata  within  a  few  seconds  or  minutes  of 
one  another. 

Each  spore  is  shot  out  violently  from  its  sterigma  to  a  distance  of  about 


CHAPTER  XII.  —  The  propelling  force  during  spore-discharge  seems  to 
be  provided  by  the  pressure  of  the  cell-sap  of  the  basidium  upon  the  cell- 
wall,  and  possibly  by  a  similar  pressure  in  the  spore.  On  the  discharge 
of  a  spore,  the  sterigma  breaks  across  but  does  not  open.  Spore-discharge 
in  the  Hymenomycetes  appears  to  resemble  that  in  Empusa  Grylli,  and 
may  be  said  to  be  brought  about  by  a  jerking  process,  which  may  be  con- 
trasted with  the  squirting  process  of  Empusa  mnscas  and  the  Ascomycetes. 

CHAPTER  XIII.  —  The  specific  gravity  of  spores  can  be  determined 
approximately  by  using  heavy  fluids  contained  in  a  counting  apparatus, 
the  chamber  of  which  is  O'l  mm.  deep.  The  specific  gravity  of  spores  of 
Amanitopsis  vaginata  was  found  to  be  nearly  that  of  water,  namely,  1-02, 
whilst  that  of  the  much  heavier  Coprinus  plicatilis  spores  proved  to  be 
approximately  1-21. 

CHAPTER  XIV.  —  The  size  of  spores  can  be  measured  with  accuracy  and 
rapidity  by  using  a  Poynting  Plate  Micrometer.  The  apparatus  has  been 
described. 

The  average  size  of  the  spores  of  a  fruit-body  may  differ  considerably  in 
different  fruit-bodies  of  the  same  species.  This  fact  may  well  account  for 
the  want  of  agreement  of  spore  measurements  as  given  by  different 
mycologists. 

CHAPTER  XV.  —  The  rate  of  fall  of  spores  in  still  air  was  determined  for 
the  first  time.  A  small  piece  of  a  fruit-body  was  placed  in  a  vertically- 
disposed  compressor  cell.  The  falling  spores  were  observed  with  a  hori- 
zontal microscope  and  their  rate  of  fall  accurately  recorded  upon  a  revolving 
drum. 

The  first  direct  test  of  the  applicability  of  Stokes'  Law  to  the  fall  of 
microscopic  spheres  in  air  has  been  carried  out  by  determining  the  size, 


266  RESEARCHES  ON  FUNGI 

specific  gravity,  and  terminal  velocity  of  the  spherical  spores  of  AnttBtitoptu 
vafjinata.  The  rate  of  fall  of  the  spores  was  found  to  be  about  46  per  cent, 
greater  than  was  expected.  While,  therefore,  the  observed  speed  has  proved 
to  be  of  the  same  order  of  magnitude  as  the  calculated,  Stokes'  Law  has  not 
been  confirmed  in  detail.  No  fully  satisfactory  reason  for  the  discrepancy 
between  theory  and  observation  has  so  far  been  found. 

CHAPTERS  XV.  AND  XVI. — The  rate  of  fall  of  hymenomycetous  spores 
ranges  from  0'3  to  6'0  mm.  per  second.  It  varies  with  the  size  of  the 
spores,  their  specific  gravity,  and  the  progress  of  desiccation.  The  rela- 
tively very  small  spores  of  Collybia  dryophila  in  very  dry  air  was  found  to 
fall  at  an  average  rate  of  0*37  mm.  per  second,  whilst  the  relatively  very 
large  spores  of  Amanitopsis  vaginata  in  a  saturated  chamber  attained  a 
speed  of  6'08  mm.  per  second.  The  spores  of  the  Mushroom  (Psalliota 
campestris),  shortly  after  they  have  left  the  pileus,  fall  at  a  speed  of 
approximately  1  mm.  per  second. 

CHAPTER  XVI. — The  spores  fall  most  rapidly  between  gills,  down  tubes, 
&c.,  immediately  after  liberation  from  the  sterigmata.  After  emerging 
from  the  fruit-bodies,  they  dry  up  within  about  one  minute.  The  diminu- 
tion of  volume  causes  a  considerable  reduction  in  the  rate  of  fall. 

CHAPTER  XVII. — The  importance  of  violent  spore-discharge  lies  in  the 
fact  that  thereby  the  very  adhesive  spores  are  prevented  from  touching  one 
another  or  any  part  of  the  hymenium  whilst  escaping  from  the  fruit-body. 
Each  spore  is  shot  out  more  or  less  horizontally  into  the  spaces  between 
the  gills,  in  hymenial  tubes,  &c.  The  horizontal  motion  is  very  rapidly 
brought  to  an  end  owing  to  the  resistance  of  the  air.  In  consequence  of 
this,  and  also  of  the  attraction  of  gravitation,  the  spore  describes  a  sharp 
curve  and  then  falls  vertically  downwards. 

The  path  of  the  spore  between  the  gills,  in  tubes,  &c.,  has  been  called 
the  sporabola,  and  is  remarkable  in  that  it  appears  to  make  a  sudden  bend 
approximately  through  a  right  angle.  When  for  any  spore  the  terminal 
vertical  velocity  and  the  maximum  horizontal  distance  of  discharge  have 
been  determined,  its  sporabola  becomes  amenable  to  a  satisfactory  mathe- 
matical treatment.  It  was  observed  that  the  spores  of  Amanitopsis  vaginata 
are  shot  outwards  from  the  gills  in  a  horizontal  direction  to  a  maximal 
distance  of  0'2  mm.  It  was  calculated  that  they  complete  this  movement 
in  approximately  ^^  second,  and  leave  the  sterigmata  with  an  initial 
horizontal  velocity  of  approximately  40  cm.  per  second.  The  steady,  ter- 
minal, vertical  velocity  of  about  0'5  cm.  per  second  is  attained  by  the  time 
a  spore  has  fallen  a  distance  equal  to  its  own  diameter,  i.e.  about  10  [j.. 

CHAPTER  XVIII. — At  the  moment  of  discharge,  or  within  a  few  seconds 


GENERAL  SUMMARY  267 

afterwards,  the  majority  of  spores  of  the  Mushroom,  (fee.,  become  electrically 
charged.  The  charges  are  relatively  of  different  strengths,  and  either 
positive  or  negative.  A  few  spores  appear  to  be  unelectrified.  No  bio- 
logical significance  has  been  ascribed  to  these  facts. 

CHAPTER  XIX. — In  the  Agaricineae  there  are  two  distinct  spore-produc- 
ing and  spore-liberating  types  of  fruit-body — the  Coprinus  comatus  type  and 
the  Mushroom  type.  These  differ  from  one  another  in  several  structural 
and  developmental  details. 

In  the  Coprini  "  deliquescence "  is  a  process  of  autodigestion  which 
renders  important  mechanical  assistance  in  the  process  of  spore-discharge. 
Jt  was  more  especially  studied  in  the  case  of  Coprinus  comatus.  The  spores 
on  each  gill  ripen  and  'are  discharged  in  succession  from  below  upwards. 
Autodigestion  leads  to  the  removal  of  those  parts  of  the  gills  which  have 
already  shed  their  spores  and  thus  permits  of  the  continued  opening  out  of 
the  pileus.  By  this  means  the  necessary  spaces  for  the  violent  discharge 
of  the  spores  from  the  basidia  are  provided.  The  spores,  after  describing 
sporabolas,  fall  vertically  downwards  between  the  gills.  On  emerging  from 
the  pileus  they  are  scattered  by  the  winds.  "  Deliquescence  "  is  in  no  way 
connected  with  the  visits  of  insects  to  the  fruit-bodies. 

The  genus  Coprinus  may  be  regarded  as  a  specialised  offshoot  from 
a  more  generalised  fungus  of  the  Mushroom  type.  There  appears  to  be 
no  satisfactory  evidence  in  support  of  Massee's  view  that  "  in  the  genus 
Coprinus  we  have  in  reality  the  remnant  of  a  primitive  group  from  which 
have  descended  the  entire  group  of  Agaricinese." 

CHAPTER  XX. — One  of  the  chief  functions  of  the  stipe  is  to  provide 
a  space  usually  one  or  more  inches  high  between  the  under  surface  of  the 
pileus  and  the  substratum  on  which  the  fruit-body  may  grow.  Owing  to 
the  very  small  rate  of  fall  of  the  spores  and  the  relatively  very  much 
greater  average  horizontal  speed  of  air-currents  near  the  ground,  the 
space  is  amply  sufficient  under  normal  conditions  to  permit  of  the  falling 
spores  being  carried  away  from  the  fruit-body  and  deposited  at  a  distance 
from  it. 

Falck's  theory,  that  the  heat  produced  in  pilei  by  respiration  and  in 
consequence  of  the  presence  of  maggots  is  of  importance  in  creating  con- 
vection currents  which  scatter  the  spores,  has  been  discussed.  If  partially 
true,  it  is  of  limited  application,  and  further  investigations  are  necessary 
in  order  to  decide  its  value. 

CHAPTER  XXI.  —  Coprophilous  Hymenomycetes  have  fruit-bodies 
adapted  to  their  peculiar  habitat  both  in  form  and  in  reactions  to  external 
stimuli. 


268  RESEARCHES   ON  FUNGI 

Slugs  are  probably  of  but  minor  importance  in  dispersing  the  spores  of 
Hymenomycetes. 

Slugs  do  not  find  the  fruit-bodies  of  all  Agaricin*  equally  palatable, 
but  prefer  to  starve  rather  than  eat  those  of  certain  species. 


PART   II 

CHAPTER  I. — The  spores  of  some  Discomycetes  (Peziza,  Bulgaria, 
Gyromitra,  &c.)  are  scattered  by  the  wind,  whilst  others  (Ascobolus  immersus, 
Saccobolus,  &c.)  are  dispersed  by  herbivorous  animals.  Each  mode  of 
spore-dispersion  is  correlated  with  special  adaptations  in  the  asci. 

The  spores  of  Peziza  repanda  are  shot  up  into  the  air  to  a  height  of 
2-3  cm.  The  eight  spores  from  an  ascus  separate  from  one  another  almost 
immediately  after  leaving  the  ascus  mouth,  and  are  then  carried  off  by  the 
wind.  The  fact  that  the  ascus  jet  breaks  up  on  leaving  the  ascus  was 
observed  by  means  of  the  beam-of-light  method. 

Puffing  is  probably  not  due  (as  de  Bary  supposed)  to  the  mere  with- 
drawal of  water  from  asci.  Solutions  of  grape  sugar,  glycerine,  sodium 
chloride,  and  potassium  nitrate,  which  merely  withdraw  water  from  the 
ripe  asci  of  Peziza  rrpanda,  do  not  cause  their  explosion.  On  the  other 
hand,  solutions  of  many  poisonous  substances,  e.g.  iodine,  mercuric  chloride, 
silver  nitrate,  copper  sulphate,  sulphuric  acid,  acetic  acid,  and  alcohol,  give 
rise  to  marked  puffing.  Two  alkalies — sodium  hydrate  and  sodium  car- 
bonate— kill  the  asci  without  causing  them  to  discharge  their  contents. 
It  seems  probable  that  puffing  is  caused  by  a  stimulus  given  to  the  proto- 
plasm in  contact  with  the  ascus  lid. 

The  physics  of  the  ascus  jet  in  Peziza  repanda  has  been  discussed.  It 
seems  probable  that  the  separation  of  the  eight  spores  of  an  ascus  during 
their  upward  flight  into  the  air  is  due  to  considerable  differences  in  the 
initial  velocities  given  to  the  individual  spores  upon  their  discharge. 
Surface  tension  probably  plays  but  a  minor  part  in  breaking  up  the  ascus 
jet.  When  the  ascus  is  regarded  as  an  apparatus  for  squirting  out  a  jet 
in  such  a  manner  that  the  jet  immediately  breaks  up  into  eight  parts  so 
that  each  part  contains  a  spore,  its  structure  becomes  more  intelligible. 

The  eight  spores  in  an  ascus  of  Peziza  repanda  are  loosely  attached 
together,  and  the  row  of  spores  is  anchored  to  the  ascus  lid  by  a  special 
protoplasmic  bridle.  De  Bary's  hypothesis  of  currents  is  unnecessary  in 
accounting  for  the  means  by  which  the  spores  are  caused  to  take  up  their 
characteristic  positions  in  the  ascus. 

The  wind-borne  spores  of  Ascomycetes  and  of  Hymenomycetes  are 
of  the  same  order  of  magnitude  with  respect  to  their  short  diameters, 
and  are  therefore  equally  well  adapted  to  be  dispersed  by  ordinary  air 
movements. 


GENERAL  SUMMARY  269 

The  Hymenomycetes,  owing  to  the  possession  of  basidia,  are  better 
organised  for  the  production  of  large  fruit-bodies  which  discharge  their 
spores  into  the  air  than  Ascomycetes.  This  is  due  to  the  fact  that, 
without  interfering  with  the  escape  of  the  spores,  a  hymenium  contain- 
ing basidia  can  be  more  compactly  folded  than  one  containing  asci. 
The  present  dominance  of  large-fruited  Hymenomycetes  over  large- 
fruited  Ascomycetes  in  forests  and  fields  may  be  indirectly  due  to  the 
fundamental  difference  between  basidia  and  asci  as  spore-discharging 
mechanisms. 

CHAPTER  II. — Ascobolus  immersus  is  specially  adapted  to  a  coprophilous 
^mode  of  existence.  The  special  adaptations  of  its  fruit-bodies  are  :  (1)  The 
protrusion  of  the  ripe -asci  beyond  the  general  surface  of  the  hymenium, 

(2)  the  diurnal  periodicity  in  the  ripening  of  successive  groups  of  asci, 

(3)  the  positive  heliotropism  of  the  asci,  (4)  the  considerable  distance  to 
which  the  spores  are  ejected  (sometimes  30  cm.) — with  which  is  associated 
(5)  the  large  size  of  the  asci  and  spores,  and  (6)  the  clinging  of  the  eight 
spores  together  whilst  describing  their  trajectory  through  the  air.      The 
adaptations  are  such  as  to  permit  of  the  asci  discharging  their  contents 
so  that  these  may  be  shot  outwards  clear   of  immediate  obstacles,  such 
as  dung  balls,  «fec.,  and  fall  on  the  surrounding  grass  where  they  may  be 
swallowed  by  herbivorous  animals. 

The  projectiles  of  Ascobolus  immersus,  Empusa,  and  Pilobolus  are  much 
larger  than  those  of  the  Hymenomycetes.  The  distance  to  which  they  are 
ejected  is  proportional  to  their  size. 

The  clinging  together  of  the  eight  spores  in  the  ascus  of  Ascobolus 
immersus  involves  an  increase  in  the  mass  of  the  projectile,  and  thereby 
enables  the  spores  to  be  shot  to  a  greater  distance  than  that  to  which  they 
would  be  shot  if  they  separated  from  one  another  immediately  after  leaving 
the  ascus  mouth. 

When  sporangiophores  of  Pilobolus  longipes  are  inclined  upwards  at  an 
angle  of  about  45°,  the  sporangia  are  often  thrown  to  a  horizontal  distance 
of  5  feet.  The  maximum  horizontal  distance  of  ejection  observed  was 
6  feet  2  inches. 

Grove's  observation  that  the  sound  of  the  discharge  of  the  sporangia 
from  the  sporangiophores  is  audible,  has  been  confirmed.  Another  sound 
can  be  detected  when  the  sporangia  strike  against  a  glass  vessel  or  a  piece 
of  paper.  The  impingement  of  sporangia  upon  a  tissue  paper  drum  could 
be  distinctly  heard  at  a  distance  of  21  feet. 

Attempts  to  detect  a  sound  proceeding  from  fruit-bodies  of  the  Mush- 
room and  Polyporus  squamosus,  when  discharging  about  a  million  spores 
a  minute,  failed.  Probably  for  unaided  human  ears,  the  liberation  of  the 
spores  of  Hymenomycetes  will  for  ever  remain  a  quite  silent  process. 


EXPLANATION    OF    PLATES    l.-V 


PLATE   I 

FIG.  1 — Coprinus  comatus.  Vertical  section  through  a  large  fruit-body  showing 
the  thin  flesh,  the  vertically-placed  gills,  darkening  from  below  upwards,  and  the 
hollow  stipe,  m,  marginal  band  covered  with  cystidia.  Natural  size. 

FIG.  2. — Psalliota  campestris.  Section  through  a  ripe  fruit-body  at  maturity  to 
be  contrasted  with  that  of  Coprinus  comatus  in  Fig.  1.  Its  flesh  is  thick,  and  the 
gills  are  nearly  horizontally  outstretched.  Specimen  obtained  from  a  field. 
Natural  size. 

FJG.  3. — Section  through  the  hymenium  of  Polyporus  squamosus,  constructed 
from  sketches  made  with  a  camera  lucida.  «,  a  basidium  with  unripe  spores  ;  b, 
a  basidium  with  ripe  spores  ;  c,  a  basidium  with  two  of  its  spores  already  dis- 
charged ;  d,  a  basidium  which  has  discharged  all  four  spores.  Paraphyses  separate 
the  basidia.  Magnification,  625. 

FIG.  4. — Psalliota  campestris.  Vertical  and  transverse  section  through  three 
gills.  The  hymenial  surfaces  are  almost  vertical.  The  arrows  indicate  the  spora- 
bolas  or  paths  described  by  spores  after  violent  discharge  from  the  sterigmata. 
Each  spore  is  shot  outwards  horizontally  to  a  distance  of  (H-0'2  mm.,  and  after 
making  a  sharp  turn  falls  vertically  downwards  in  the  space  between  the  gills. 
Magnification,  25. 

FIG.  5. — Coprinus  comatus.  Transverse  section  through  some  of  the  gills 
whilst  the  spores  are  ripening,  s,  s,  spaces  between  the  gills  lined  by  the 
hymenium ;  e,  inner  swollen  edges  of  gills  covered  with  cystidia  ;  /,  pileus  flesh. 
Magnification,  8. 

PLATE    II 

Figs,  all  of  Coprinus  comatus. 

FlG.  6. — Vertical  section  through  a  young  fruit-body  shortly  after  it  had 
appeared  above  the  ground,  s,  level  of  soil.  Natural  size. 

FIG.  7. — Vertical  section  through  an  older  fruit-body  shortly  before  the  gills 
separate  from  the  stipe,  s,  level  of  soil.  Natural  size. 

FIG.  8. — Vertical  section  through  a  fruit-body  after  autodigestion  has  begun. 
The  gills  are  becoming  liquefied  from  below  upwards.  The  dotted  lines  show  the 
shape  and  position  of  the  gills  at  the  moment  autodigestion  began,  s,  lower 
edge  of  gill  where  spore-discharge  and  subsequently  autodigestion  first  become 
active  ;  «,  oblique  edge  of  gill  where  spore-discharge  and  autodigestion  are  taking 
place  ;  m,  marginal  band  on  gill  edge  covered  with  cystidia.  Natural  size. 

FIG.  9. — Vertical  section  through  a  fruit-body  which  has  become  helmet- 
shaped.  By  autodigestion  the  gills  have  now  become  reduced  to  about  one-third 
their  original  length.  «,  edge  of  gill  where  spore-liberation  and  autodigestion 

270 


EXPLANATION   OF  PLATES  271 

are  still  in  progress,  m,  marginal  band  on  gill  edge  covered  with  cystidia. 
Natural  size. 

FIG.  10. — Vertical  section  through  a  fruit-body  when  autodigestion  is  nearly 
completed.  The  remains  of  the  gills  have  now  become  horizontally  outstretched. 
Liquid  drops  may  be  seen  at  d  in  such  a  position  that  they  do  not  interfere  with 
the  liberation  of  the  spores  into  the  air.  a,  edge  of  gill  where  spore-liberation 
and  autodigestion  are  still  in  progress,  m,  marginal  band  on  gill  edge  covered 
with  cystidia.  Natural  size. 

FIG.  11.— Fruit-body  in  the  last  stage  when  spore-liberation  has  ceased.  The 
gills  have  now  entirely  disappeared.  The  central  part  of  the  pileus  flesh  still 
crowns  the  stipe.  Natural  size. 

FIG.  12. — Semi-diagrammatic  drawing  of  part  of  a  gill  surface  m  the  region  of 
autodigestion.  There  are  five  zones  running  parallel  to  the  oblique  gill  edges : 
(1)  a-af,  zone  of  basidiawith  ripe  spores.  (2)  b-b',  zone  of  basidia  discharging  spores 
into  an  interlamellar  space.  The  spores  are  shot  off  their  sterigmata  successively, 
so  that  in  this  zone  some  basidia  have  three  spores  left  upon  them,  some  two,  and 
some  one,  whilst  some  have  lost  them  all.  (3)  c-c',  zone  of  basidia  which  have  dis- 
charged all  their  spores.  (4)  d-d',  zone  of  autodigestion.  The  basidia  and  para- 
physes  are  becoming  indistinct  and  gradually  liquefied.  (5)  e-e',  the  dark  liquid 
film  on  the  gill  edge  containing  the  products  of  autodigestion.  Magnification, 
320. 

PLATE    III 

Figs.   13-17  all  of  C'oprinus  comatus. 

FIG.  13. — Surface  view  of  part  of  one  side  of  the  inner  swollen  edge  of  a  gill 
before  autodigestion  has  begun,  m,  marginal  band  covered  with  cystidia,  c ; 
h,  hymenium  containing  basidia  with  ripe  spores.  Magnification,  1 20. 

FIG.  14. — Transverse  section  through  the  inner  swollen  edges  of  three  gills 
before  autodigestion  has  begun.  The  swollen  edges  contain  large  air-spaces,  a  a, 
and  are  covered  by  cystidia,  c.  The  spaces  s  s  between  the  gills  are  lined  by  the 
hymenium.  The  basidia  each  bear  four  spores;  but  of  these,  for  the  sake  of 
clearness,  two  only  are  shown.  Magnification,  120. 

FIG.  15.  —  Surface  view  of  a  piece  of  gill,  O'Ol  mm.  by  0*02  mm.,  in 
the  region  of  ripe  spores  close  to  the  zone  of  spore-discharge.  Each  basidium 
bears  four  black  spores,  and  is  separated  from  its  neighbours  by  paraphyses. 
Magnification,  320. 

FIG.  16. — Section  through  the  hymenium  in  the  region  of  spore-discharge. 
The  two  uppermost  basidia  each  bear  four  ripe  spores ;  the  middle  basidium  has 
discharged  two  spores,  the  next  below  that  three  spores,  and  the  lowest  basidium 
of  all  four  spores.  Two  sporabolic  paths,  one  with  the  horizontal  distance  O'l  mm. 
long  and  the  other  with  it  0'15  mm.  long,  are  also  shown.  Magnification,  320. 

FIG.  17. — Diagram  showing  the  paths  of  spores  during  discharge  from  the  gills. 
A,  transverse  section  cut  horizontally  through  three  gills.  The  dark,  free  edges 
are  covered  by  liquid  films  produced  by  autodigestion.  The  arrows  show  the 
direction  in  which  the  spores  are  discharged  from  the  zones  of  spore-discharge, 
and  also  the  distance  to  which  they  travel  horizontally.  B  shows  a  piece  of  one 
of  the  gills  seen  from  the  side.  The  arrows  indicate  by  their  positions  and  direc- 
tions the  vertical  paths  of  the  spores  after  leaving  the  zone  of  spore-discharge. 


272  RESEARCHES   ON  FUNGI 

C  shows  the  appearance  of  the  three  gills  when  looked  at  edgewise  from  the  stipe. 
The  arrows  indicate  the  sporabolas  or  paths  taken  by  the  spores  when  escaping 
from  the  gills. 

Figs.   18-20  all  of  Coprinus  micaceus. 

FIG.  18. — Young  fruit-body  from  which  spore-liberation  has  begun.  Natural 
size. 

FIG.  19. — Vertical  section  through  a  young  fruit-body  before  spore-liberation 
has  begun.  The  gills  are  turning  brown  and  ripening  their  spores  from  below 
upwards.  Natural  size. 

FIG.  20. — a,  ft,  c,  and  d.  Successive  stages  during  the  autodigestion  of  the 
gills.  Drawn  from  four  different  fruit-bodies.  Natural  size. 


PLATE    IV 

Figs.  21-24  all  of  Coprinus  comatus. 

FIG.  21. — Characteristic  group  of  fruit-bodies  growing  in  a  field.  Owing  to 
excessive  crowding,  parts  of  the  free  margin  of  the  pileus  of  two  individuals  have 
stuck  to  younger  fruit-bodies.  Magnification  about  6. 

FIG.  22. — Specimens  placed  in  a  row  and  photographed  to  show  the  various 
stages  of  development.  The  gradual  opening  out  of  the  pileus  and  the  curling  up 
of  its  free  margin  during  autodigestion,  and  also  the  lengthening  of  the  stipe, 
may  be  traced  from  right  to  left.  Magnification  about  7. 

FIG.  23. — Underside  of  a  fruit-body  liberating  spores.  Autodigestion  is 
taking  place  where  the  gills  look  black  and  are  evidently  separated  by  free 
spaces.  Spores  are  being  discharged  into  the  air  from  hymenial  zones  just  above 
and  parallel  to  the  wet  gill  edges.  The  inner  and  higher  parts  of  the  gills,  where 
autodigestion  is  not  yet  taking  place,  are  still  united  at  their  edges  by  the  large 
white  cystidia.  Natural  size. 

FIG.  24. — Photograph  of  a  helmet-shaped  fruit-body  in  a  field.  A  marked 
feature  is  the  outwardly  folded  remains  of  the  gills  at  the  free  margin  of  the 
pileus.  A  drop  of  "  ink  "  hangs  from  the  pileus  opposite  the  stipe.  The  dark 
liquid  drop  is  in  such  a  position  that  it  does  not  interfere  with  the  discharge  of 
the  spores  into  the  air.  Magnification  about  ^. 

FIG.  25. — View  of  the  underside  of  a  mature  pileus  of  Psalliota  campestris 
grown  on  a  Mushroom  bed.  The  gills  are  horizontally  outstretched  and  free 
from  each  other  throughout  their  length.  Spores  are  liberated  from  all  the  inter- 
lamellar  spaces  and  from  every  part  of  them  simultaneously.  Natural  size. 

FIG.  26. — The  Poynting  Plate  Micrometer  and  a  microscope  for  using  it.  The 
glass  plate,  p,  can  be  pushed  into  the  slot  si.  The  stand,  st,  has  a  vertical  arm,  a, 
with  a  scale,  sc.  The  plate,  p,  is  attached  to  the  horizontal  rod,  r,  which  can  be 
rotated  by  means  of  the  lever,  I,  which  terminates  in  a  small  framework  carrying 
a  piece  of  glass  on  which  is  etched  a  line  parallel  to  the  lever.  For  further 
description  see  the  text. 

FIG.  27. — Polyporus  squamosus.  Spore-deposit  made  in  about  twenty-four 
hours  from  the  hymenial  tubes  of  a  piece  of  the  pileus.  Each  tube  has  produced 
its  own  heap  of  spores.  Natural  size. 

FIG.    28. — Polyporus  squamosus.      Spore-deposit   made   in    about  twenty-four 


EXPLANATION   OF  PLATES  273 

hours  from  a  vertical  section  of  the  pileus.  Each  half-tube  has  liberated  spores 
throughout  the  whole  length  of  its  hymenium-bearing  surface.  Natural  size. 

FIG.  29. — Measurement  of  the  rate  of  fall  of  spores.  The  observer  is  looking 
through  the  horizontal  microscope  at  a  field  focussed  below  the  gills  of  a  piece  of 
pileus  contained  in  a  vertically-placed  compressor  cell  held  in  a  clip.  The  cell  is 
illuminated  by  diffuse  daylight  reflected  from  a  glass  roof  to  the  eye  by  means  of 
a  mirror.  On  the  table  to  the  right  is  placed  a  drum  driven  by  electricity.  The 
chronometer  at  the  back  is  used  for  making  time-records.  The  small  battery  on 
the  right  of  the  drum  is  connected  with  the  fountain  pen  which  touches  the  drum 
paper  as  the  latter  revolves,  and  also  with  the  tapping-key  upon  the  knob  of  which 
the  observer  has  his  first  finger.  As  a  spore  passes  the  three  eye-piece  lines  in 
tthe  field  of  view,  the  observer  makes  three  successive  taps  upon  the  tapping-key. 
The  fountain  pen  in  response  makes  three  deviations  from  its  normal  course  on 
the  paper.  Each  spore  record  is  afterwards  measured  on  the  drum  by  means  of  a 
steel  tape. 

FIG.  30. — Amanitopsis  vaginata.  A  fruit-body  photographed  in  a  wood. 
Magnification  about  £. 


PLATE   V 

Figs,  all  of  Polyporus  squamosus. 

FIGS.  31,  32,  33,  and  34. — Successive  stages  in  the  development  of  two  fruit- 
bodies  grown  on  a  log  in  the  light.  Natural  size. 

FIG.  31. — One  day  old.  A  stromatous  knob  half  hidden  in  a  rift  of  the  log  has 
developed  four  conical  processes. 

FIG.  32. — Two  days  old.  The  four  conical  processes  have  become  flattened  at 
their  ends  in  preparation  for  the  development  of  pilei. 

FIG.  33. — Three  and  a  half  days  old.  Two  of  the  conical  processes  have 
ceased  to  grow  ;  the  other  two  have  become  converted  into  young  fruit-bodies. 
These  have  obliquely-placed  stipes,  and  their  pilei,  which  at  first  were  sym- 
metrically developed,  already  show  distinct  signs  of  eccentricity.  The  growth  of 
the  stipes  has  raised  the  pilei  so  that  their  upper  surfaces  have  now  come  to  lie 
in  a  horizontal  plane. 

FIG.  34. — Nearly  five  days  old.  The  eccentricity  of  the  pilei  and  their  growth 
in  a  horizontal  plane  have  become  very  marked.  The  posterior  sides  of  the  pilei 
are  in  contact  and  have  now  ceased  to  develop.  The  stipes  have  attained  their 
maximum  size. 

When  seven  days  old  the  fruit-bodies  were  fully  extended  and  shedding  spores 
abundantly,  although  the  hymenial  tubes  had  not  yet  reached  their  maximum 
length.  The  left-hand  pileus  had  become  1 1  cm.  wide  from  the  posterior  to  the 
anterior  edge,  and  the  right-hand  one  9  cm.  wide.  When  looked  at  from  above, 
both  pilei  appeared  very  eccentric  and  resembled  the  pileus  shown  in  Fig.  4  in 
the  text  (p.  28).  The  last  stage  is  shown  in  Fig.  34  in  the  text  (p.  84). 

FIG.  35. — Young  fruit-body  about  three  days  old.  It  has  developed  from  the 
only  conical  process  produced  by  the  stromatous  knob.  The  pileus  is  very 
centric.  Natural  size. 

FIG.  36. — Stromatous  knob  giving  rise  to  a  number  of  conical  processes  in  the 
dark.  Natural  size. 

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